Refactor build script toolchain lookups.

Now environment variable overrides no longer infect the build scripts.

_toolchain.overrides is dropped as probably misguided in the first place.

Fixes #251.

nmigen/vendor/intel.py

@@ -103,22 +103,22 @@ class IntelPlatform(TemplatedPlatform):
     }
     command_templates = [
         r"""
-        {{get_tool("quartus_map")}}
+        {{invoke_tool("quartus_map")}}
             {{get_override("quartus_map_opts")|options}}
             --rev={{name}} {{name}}
         """,
         r"""
-        {{get_tool("quartus_fit")}}
+        {{invoke_tool("quartus_fit")}}
             {{get_override("quartus_fit_opts")|options}}
             --rev={{name}} {{name}}
         """,
         r"""
-        {{get_tool("quartus_asm")}}
+        {{invoke_tool("quartus_asm")}}
             {{get_override("quartus_asm_opts")|options}}
             --rev={{name}} {{name}}
         """,
         r"""
-        {{get_tool("quartus_sta")}}
+        {{invoke_tool("quartus_sta")}}
             {{get_override("quartus_sta_opts")|options}}
             --rev={{name}} {{name}}
         """,

nmigen/vendor/lattice_ecp5.py

@@ -136,14 +136,14 @@ class LatticeECP5Platform(TemplatedPlatform):
     }
     _trellis_command_templates = [
         r"""
-        {{get_tool("yosys")}}
+        {{invoke_tool("yosys")}}
             {{quiet("-q")}}
             {{get_override("yosys_opts")|options}}
             -l {{name}}.rpt
             {{name}}.ys
         """,
         r"""
-        {{get_tool("nextpnr-ecp5")}}
+        {{invoke_tool("nextpnr-ecp5")}}
             {{quiet("--quiet")}}
             {{get_override("nextpnr_opts")|options}}
             --log {{name}}.tim
@@ -155,7 +155,7 @@ class LatticeECP5Platform(TemplatedPlatform):
             --textcfg {{name}}.config
         """,
         r"""
-        {{get_tool("ecppack")}}
+        {{invoke_tool("ecppack")}}
             {{verbose("--verbose")}}
             {{get_override("ecppack_opts")|options}}
             --input {{name}}.config
@@ -235,16 +235,16 @@ class LatticeECP5Platform(TemplatedPlatform):
     _diamond_command_templates = [
         # These don't have any usable command-line option overrides.
         r"""
-        {{get_tool("pnmainc")}}
+        {{invoke_tool("pnmainc")}}
             {{name}}.tcl
         """,
         r"""
-        {{get_tool("ddtcmd")}}
+        {{invoke_tool("ddtcmd")}}
             -oft -bit
             -if {{name}}_impl/{{name}}_impl.bit -of {{name}}.bit
         """,
         r"""
-        {{get_tool("ddtcmd")}}
+        {{invoke_tool("ddtcmd")}}
             -oft -svfsingle -revd -op "Fast Program"
             -if {{name}}_impl/{{name}}_impl.bit -of {{name}}.svf
         """,

nmigen/vendor/lattice_ice40.py

@@ -140,14 +140,14 @@ class LatticeICE40Platform(TemplatedPlatform):
     }
     _icestorm_command_templates = [
         r"""
-        {{get_tool("yosys")}}
+        {{invoke_tool("yosys")}}
             {{quiet("-q")}}
             {{get_override("yosys_opts")|options}}
             -l {{name}}.rpt
             {{name}}.ys
         """,
         r"""
-        {{get_tool("nextpnr-ice40")}}
+        {{invoke_tool("nextpnr-ice40")}}
             {{quiet("--quiet")}}
             {{get_override("nextpnr_opts")|options}}
             --log {{name}}.tim
@@ -160,7 +160,7 @@ class LatticeICE40Platform(TemplatedPlatform):
             --asc {{name}}.asc
         """,
         r"""
-        {{get_tool("icepack")}}
+        {{invoke_tool("icepack")}}
             {{verbose("-v")}}
             {{name}}.asc
             {{name}}.bin

nmigen/vendor/lattice_machxo2.py

@@ -106,17 +106,17 @@ class LatticeMachXO2Platform(TemplatedPlatform):
     command_templates = [
         # These don't have any usable command-line option overrides.
         r"""
-        {{get_tool("pnmainc")}}
+        {{invoke_tool("pnmainc")}}
             {{name}}.tcl
         """,
         r"""
-        {{get_tool("ddtcmd")}}
+        {{invoke_tool("ddtcmd")}}
             -oft -jed
             -dev {{platform.device}}-{{platform.speed}}{{platform.package}}{{platform.grade}}
             -if {{name}}_impl/{{name}}_impl.jed -of {{name}}.jed
         """,
         r"""
-        {{get_tool("ddtcmd")}}
+        {{invoke_tool("ddtcmd")}}
             -oft -svfsingle -revd -op "FLASH Erase,Program,Verify"
             -if {{name}}_impl/{{name}}_impl.jed -of {{name}}.svf
         """,

nmigen/vendor/xilinx_7series.py

@@ -139,7 +139,7 @@ class Xilinx7SeriesPlatform(TemplatedPlatform):
     }
     command_templates = [
         r"""
-        {{get_tool("vivado")}}
+        {{invoke_tool("vivado")}}
             {{verbose("-verbose")}}
             {{get_override("vivado_opts")|options}}
             -mode batch

nmigen/vendor/xilinx_spartan_3_6.py

@@ -141,12 +141,12 @@ class XilinxSpartan3Or6Platform(TemplatedPlatform):
     }
     command_templates = [
         r"""
-        {{get_tool("xst")}}
+        {{invoke_tool("xst")}}
             {{get_override("xst_opts")|options}}
             -ifn {{name}}.xst
         """,
         r"""
-        {{get_tool("ngdbuild")}}
+        {{invoke_tool("ngdbuild")}}
             {{quiet("-quiet")}}
             {{verbose("-verbose")}}
             {{get_override("ngdbuild_opts")|options}}
@@ -154,7 +154,7 @@ class XilinxSpartan3Or6Platform(TemplatedPlatform):
             {{name}}.ngc
         """,
         r"""
-        {{get_tool("map")}}
+        {{invoke_tool("map")}}
             {{verbose("-detail")}}
             {{get_override("map_opts")|default([])|options}}
             -w
@@ -163,7 +163,7 @@ class XilinxSpartan3Or6Platform(TemplatedPlatform):
             {{name}}.pcf
         """,
         r"""
-        {{get_tool("par")}}
+        {{invoke_tool("par")}}
             {{get_override("par_opts")|default([])|options}}
             -w
             {{name}}_map.ncd
@@ -171,7 +171,7 @@ class XilinxSpartan3Or6Platform(TemplatedPlatform):
             {{name}}.pcf
         """,
         r"""
-        {{get_tool("bitgen")}}
+        {{invoke_tool("bitgen")}}
             {{get_override("bitgen_opts")|default(["-g Compress"])|options}}
             -w
             -g Binary:Yes

nmigen/vendor/xilinx_ultrascale.py

@@ -139,7 +139,7 @@ class XilinxUltraScalePlatform(TemplatedPlatform):
     }
     command_templates = [
         r"""
-        {{get_tool("vivado")}}
+        {{invoke_tool("vivado")}}
             {{verbose("-verbose")}}
             {{get_override("vivado_opts")|options}}
             -mode batch