runtime: correct runtime.GOOS, runtime.GOARCH

If the same directory was used for multiple builds,
it was possible for a stale version.go to contain the
wrong definitions for $GOOS and $GOARCH, because
they can change even if the hg version does not.
Split into multiple files to fix.

R=r, r2
CC=golang-dev
https://golang.org/cl/4124050

src/pkg/runtime/Makefile

@@ -26,8 +26,12 @@ GOFILES=\
 	softfloat64.go\
 	type.go\
 	version.go\
+	version_$(GOOS).go\
+	version_$(GOARCH).go\
 	runtime_defs.go\
 
+CLEANFILES+=version.go version_*.go
+
 OFILES_windows=\
 	syscall.$O\
 
@@ -127,6 +131,12 @@ mkversion: mkversion.c
 version.go: mkversion
 	./mkversion >version.go
 
+version_$(GOARCH).go:
+	(echo 'package runtime'; echo 'const theGoarch = "$(GOARCH)"') >$@
+
+version_$(GOOS).go:
+	(echo 'package runtime'; echo 'const theGoos = "$(GOOS)"') >$@
+
 %.c:	%.goc goc2c
 	./goc2c `pwd`/$< > $@.tmp
 	mv -f $@.tmp $@

src/pkg/runtime/mkversion.c

@@ -5,13 +5,11 @@ char *template =
 	"// generated by mkversion.c; do not edit.\n"
 	"package runtime\n"
 	"const defaultGoroot = \"%s\"\n"
-	"const theVersion = \"%s\"\n"
-	"const theGoarch = \"%s\"\n"
-	"const theGoos = \"%s\"\n";
+	"const theVersion = \"%s\"\n";
 
 void
 main(void)
 {
-	print(template, getgoroot(), getgoversion(), getgoarch(), getgoos());
+	print(template, getgoroot(), getgoversion());
 	exits(0);
 }