ignore $GOARCH inside the compiler and linker.

by definition, they know what they are building for.
makes it easier to switch architectures when testing.

% 6g x.go
% 6l x.6
% 6.out
"Wed Jan 13 10:57:46 EST 2010"
% 8g x.go
% 8l x.8
% 8.out
"Wed Jan 13 10:57:46 EST 2010"
% echo $GOARCH

%

R=rsc
CC=golang-dev
https://golang.org/cl/186116

src/cmd/gc/lex.c

@@ -225,7 +225,7 @@ findpkg(Strlit *name)
 	if(goroot == nil) {
 		goroot = getenv("GOROOT");
 		goos = getenv("GOOS");
-		goarch = getenv("GOARCH");
+		goarch = thestring;
 	}
 
 	if(islocalname(name)) {

src/cmd/ld/lib.c

@@ -721,7 +721,6 @@ mywhatsys(void)
 	char *s;
 
 	goroot = getenv("GOROOT");
-	goarch = getenv("GOARCH");
 	goos = getenv("GOOS");
 
 	if(goroot == nil) {
@@ -732,9 +731,7 @@ mywhatsys(void)
 		strcpy(goroot, s);
 		strcat(goroot, "/go");
 	}
-	if(goarch == nil) {
-		goarch = "amd64";
-	}
+	goarch = thestring;	// ignore $GOARCH - we know who we are
 	if(goos == nil) {
 		goos = "linux";
 	}

src/cmd/ld/lib.h

@@ -52,6 +52,7 @@ EXTERN	uchar	inuxi4[4];
 EXTERN	uchar	inuxi8[8];
 EXTERN	char*	outfile;
 EXTERN	int32	nsymbol;
+EXTERN	char*	thestring;
 
 void	addlib(char *src, char *obj);
 void	copyhistfrog(char *buf, int nbuf);