cmd/gc: support -installsuffix in the compiler and builder

Add the -installsuffix flag to gc and {5,6,8}l, which overrides -race
for the suffix if both are supplied.
Pass this flag from the go tool for build and install.

R=rsc
CC=golang-dev
https://golang.org/cl/14246044

src/cmd/5l/obj.c

@@ -117,6 +117,7 @@ main(int argc, char *argv[])
 	flagstr("extldflags", "flags for external linker", &extldflags);
 	flagcount("f", "ignore version mismatch", &debug['f']);
 	flagcount("g", "disable go package data checks", &debug['g']);
+	flagstr("installsuffix", "pkg directory suffix", &flag_installsuffix);
 	flagstr("k", "sym: set field tracking symbol", &tracksym);
 	flagfn1("linkmode", "mode: set link mode (internal, external, auto)", setlinkmode);
 	flagcount("n", "dump symbol table", &debug['n']);

src/cmd/6l/obj.c

@@ -112,6 +112,7 @@ main(int argc, char *argv[])
 	flagstr("extldflags", "flags for external linker", &extldflags);
 	flagcount("f", "ignore version mismatch", &debug['f']);
 	flagcount("g", "disable go package data checks", &debug['g']);
+	flagstr("installsuffix", "pkg directory suffix", &flag_installsuffix);
 	flagfn1("linkmode", "mode: set link mode (internal, external, auto)", setlinkmode);
 	flagstr("k", "sym: set field tracking symbol", &tracksym);
 	flagcount("n", "dump symbol table", &debug['n']);

src/cmd/8l/obj.c

@@ -118,6 +118,7 @@ main(int argc, char *argv[])
 	flagstr("extldflags", "flags for external linker", &extldflags);
 	flagcount("f", "ignore version mismatch", &debug['f']);
 	flagcount("g", "disable go package data checks", &debug['g']);
+	flagstr("installsuffix", "pkg directory suffix", &flag_installsuffix);
 	flagfn1("linkmode", "mode: set link mode (internal, external, auto)", setlinkmode);
 	flagstr("k", "sym: set field tracking symbol", &tracksym);
 	flagstr("o", "outfile: set output file", &outfile);

src/cmd/gc/go.h

@@ -976,6 +976,7 @@ EXTERN	int	typecheckok;
 EXTERN	int	compiling_runtime;
 EXTERN	int	compiling_wrappers;
 EXTERN	int	pure_go;
+EXTERN	char*	flag_installsuffix;
 EXTERN	int	flag_race;
 EXTERN	int	flag_largemodel;
 EXTERN	int	noescape;

src/cmd/gc/lex.c

@@ -257,6 +257,7 @@ main(int argc, char *argv[])
 	flagcount("g", "debug code generation", &debug['g']);
 	flagcount("h", "halt on error", &debug['h']);
 	flagcount("i", "debug line number stack", &debug['i']);
+	flagstr("installsuffix", "pkg directory suffix", &flag_installsuffix);
 	flagcount("j", "debug runtime-initialized variables", &debug['j']);
 	flagcount("l", "disable inlining", &debug['l']);
 	flagcount("m", "print optimization decisions", &debug['m']);
@@ -577,7 +578,7 @@ static int
 findpkg(Strlit *name)
 {
 	Idir *p;
-	char *q, *race;
+	char *q, *suffix, *suffixsep;
 
 	if(islocalname(name)) {
 		if(safemode)
@@ -615,13 +616,19 @@ findpkg(Strlit *name)
 			return 1;
 	}
 	if(goroot != nil) {
-		race = "";
-		if(flag_race)
-			race = "_race";
-		snprint(namebuf, sizeof(namebuf), "%s/pkg/%s_%s%s/%Z.a", goroot, goos, goarch, race, name);
+		suffix = "";
+		suffixsep = "";
+		if(flag_installsuffix != nil) {
+			suffixsep = "_";
+			suffix = flag_installsuffix;
+		} else if(flag_race) {
+			suffixsep = "_";
+			suffix = "race";
+		}
+		snprint(namebuf, sizeof(namebuf), "%s/pkg/%s_%s%s%s/%Z.a", goroot, goos, goarch, suffixsep, suffix, name);
 		if(access(namebuf, 0) >= 0)
 			return 1;
-		snprint(namebuf, sizeof(namebuf), "%s/pkg/%s_%s%s/%Z.%c", goroot, goos, goarch, race, name, thechar);
+		snprint(namebuf, sizeof(namebuf), "%s/pkg/%s_%s%s%s/%Z.%c", goroot, goos, goarch, suffixsep, suffix, name, thechar);
 		if(access(namebuf, 0) >= 0)
 			return 1;
 	}

src/cmd/go/build.go

@@ -1530,6 +1530,9 @@ func (gcToolchain) gc(b *builder, p *Package, obj string, importArgs []string, g
 	if extFiles == 0 {
 		gcargs = append(gcargs, "-complete")
 	}
+	if buildContext.InstallSuffix != "" {
+		gcargs = append(gcargs, "-installsuffix", buildContext.InstallSuffix)
+	}
 
 	args := stringList(tool(archChar+"g"), "-o", ofile, buildGcflags, gcargs, "-D", p.localPrefix, importArgs)
 	for _, f := range gofiles {
@@ -1579,6 +1582,9 @@ func (gcToolchain) ld(b *builder, p *Package, out string, allactions []*action,
 		}
 	}
 	ldflags := buildLdflags
+	if buildContext.InstallSuffix != "" {
+		ldflags = append(ldflags, "-installsuffix", buildContext.InstallSuffix)
+	}
 	if cxx {
 		// The program includes C++ code.  If the user has not
 		// specified the -extld option, then default to

src/cmd/go/testflag.go

@@ -82,6 +82,7 @@ var testFlagDefn = []*testFlagSpec{
 	{name: "tags"},
 	{name: "compiler"},
 	{name: "race", boolVar: &buildRace},
+	{name: "installsuffix"},
 
 	// passed to 6.out, adding a "test." prefix to the name if necessary: -v becomes -test.v.
 	{name: "bench", passToTest: true},

src/cmd/ld/lib.c

@@ -91,7 +91,7 @@ Lflag(char *arg)
 void
 libinit(void)
 {
-	char *race;
+	char *suffix, *suffixsep;
 
 	fmtinstall('i', iconv);
 	fmtinstall('Y', Yconv);
@@ -101,10 +101,16 @@ libinit(void)
 		print("goarch is not known: %s\n", goarch);
 
 	// add goroot to the end of the libdir list.
-	race = "";
-	if(flag_race)
-		race = "_race";
-	Lflag(smprint("%s/pkg/%s_%s%s", goroot, goos, goarch, race));
+	suffix = "";
+	suffixsep = "";
+	if(flag_installsuffix != nil) {
+		suffixsep = "_";
+		suffix = flag_installsuffix;
+	} else if(flag_race) {
+		suffixsep = "_";
+		suffix = "race";
+	}
+	Lflag(smprint("%s/pkg/%s_%s%s%s", goroot, goos, goarch, suffixsep, suffix));
 
 	// Unix doesn't like it when we write to a running (or, sometimes,
 	// recently run) binary, so remove the output file before writing it.

src/cmd/ld/lib.h

@@ -160,6 +160,7 @@ EXTERN	char**	ldflag;
 EXTERN	int	havedynamic;
 EXTERN	int	iscgo;
 EXTERN	int	elfglobalsymndx;
+EXTERN	char*	flag_installsuffix;
 EXTERN	int	flag_race;
 EXTERN	int flag_shared;
 EXTERN	char*	tracksym;