build.plat: source a script with toolchain environment.

Fixes #131.

nmigen/vendor/lattice_ecp5.py

@@ -14,6 +14,9 @@ class LatticeECP5Platform(TemplatedPlatform):
         * ``nextpnr-ecp5``
         * ``ecppack``
 
+    The environment is populated by running the script specified in the environment variable
+    ``NMIGEN_Trellis_env``, if present.
+
     Available overrides:
         * ``verbose``: enables logging of informational messages to standard error.
         * ``read_verilog_opts``: adds options for ``read_verilog`` Yosys command.
@@ -33,6 +36,8 @@ class LatticeECP5Platform(TemplatedPlatform):
         * ``{{name}}.svf``: JTAG programming vector.
     """
 
+    toolchain = "Trellis"
+
     device  = abstractproperty()
     package = abstractproperty()
     speed   = abstractproperty()

nmigen/vendor/lattice_ice40.py

@@ -14,6 +14,9 @@ class LatticeICE40Platform(TemplatedPlatform):
         * ``nextpnr-ice40``
         * ``icepack``
 
+    The environment is populated by running the script specified in the environment variable
+    ``NMIGEN_IceStorm_env``, if present.
+
     Available overrides:
         * ``verbose``: enables logging of informational messages to standard error.
         * ``read_verilog_opts``: adds options for ``read_verilog`` Yosys command.
@@ -32,6 +35,8 @@ class LatticeICE40Platform(TemplatedPlatform):
         * ``{{name}}.bin``: binary bitstream.
     """
 
+    toolchain = "IceStorm"
+
     device  = abstractproperty()
     package = abstractproperty()
 

nmigen/vendor/xilinx_7series.py

@@ -14,6 +14,9 @@ class Xilinx7SeriesPlatform(TemplatedPlatform):
     Required tools:
         * ``vivado``
 
+    The environment is populated by running the script specified in the environment variable
+    ``NMIGEN_Vivado_env``, if present.
+
     Available overrides:
         * ``script_after_read``: inserts commands after ``read_xdc`` in Tcl script.
         * ``script_after_synth``: inserts commands after ``synth_design`` in Tcl script.
@@ -42,6 +45,8 @@ class Xilinx7SeriesPlatform(TemplatedPlatform):
         * ``{{name}}.bit``: binary bitstream.
     """
 
+    toolchain = "Vivado"
+
     device  = abstractproperty()
     package = abstractproperty()
     speed   = abstractproperty()

nmigen/vendor/xilinx_spartan6.py

@@ -19,6 +19,9 @@ class XilinxSpartan6Platform(TemplatedPlatform):
             * ``par``
             * ``bitgen``
 
+    The environment is populated by running the script specified in the environment variable
+    ``NMIGEN_ISE_env``, if present.
+
     Available overrides:
         * ``script_after_run``: inserts commands after ``run`` in XST script.
         * ``add_constraints``: inserts commands in UCF file.
@@ -45,6 +48,8 @@ class XilinxSpartan6Platform(TemplatedPlatform):
         * ``{{name}}.bit``: binary bitstream.
     """
 
+    toolchain = "ISE"
+
     device  = abstractproperty()
     package = abstractproperty()
     speed   = abstractproperty()