zilch-cli-rust: provide default overrides

cli/zilch-rust.scm

@@ -1,5 +1,8 @@
 (import (scheme base) (scheme write) (zilch statusbar) (zilch nix daemon) (zilch magic) (zilch lib getopt) (scheme process-context) (chicken process-context) (srfi 146) (chicken port) (chicken foreign) (chicken condition))
 (foreign-declare "#include <sched.h>")
+(foreign-declare "#include \"stock_overrides.h\"")
+(define stock-overrides (foreign-value "stock_overrides" nonnull-c-string))
+
 (define get-cpu-count
   (foreign-lambda* int ()
     "cpu_set_t set; sched_getaffinity(0, sizeof(set), &set); C_return(CPU_COUNT(&set));"))
@@ -26,6 +29,9 @@ executables in the crate, if unspecified)
                           the upstream module. Can be specified more
                           than once.
   -z, --overrides PATH    Read build script overrides from this file.
+                          By default, a stock set of overrides is read.
+                          This can be disabled by passing `-z \"\"`
+                          (a blank string).
 
    --debug                Crash on the first error, rather than
                           continuing with the next package.
@@ -156,9 +162,14 @@ executables in the crate, if unspecified)
    (set! rustc-overrides (mapping-set! rustc-overrides crate-name (parse-inner rustc))))
   (vector->list data)))
 
+
+; If we have no request to disable stock overrides, apply them.
+(unless (member '(overrides "") options)
+  (process-overrides (call-with-port (open-input-string stock-overrides) json-read)))
+
 (for-each
  (lambda (kv)
-  (when (eq? (car kv) 'overrides) (process-overrides (call-with-input-file (cdr kv) json-read))))
+  (when (eq? (car kv) 'overrides) (unless (string=? (cdr kv) "") (process-overrides (call-with-input-file (cdr kv) json-read)))))
  options)
 
 (define (build-script-env-overrides crate-name is-dependency)