cmd/go, cmd/ld: fix libgcc order and add __image_base__ symbol for windows

        Fixes #4063.

R=alex.brainman, rsc
CC=golang-dev
https://golang.org/cl/6543066

src/cmd/go/build.go

@@ -1597,9 +1597,12 @@ func (b *builder) cgo(p *Package, cgoExe, obj string, gccfiles []string) (outGo,
 	if err != nil {
 		return nil, nil, err
 	}
-	staticLibs := []string{libgcc}
+	var staticLibs []string
 	if goos == "windows" {
-		staticLibs = append(staticLibs, "-lmingwex", "-lmingw32")
+		// libmingw32 and libmingwex might also use libgcc, so libgcc must come last
+		staticLibs = []string{"-lmingwex", "-lmingw32", libgcc}
+	} else {
+		staticLibs = []string{libgcc}
 	}
 
 	for _, cfile := range cfiles {

src/cmd/ld/pe.c

@@ -148,6 +148,9 @@ peinit(void)
 	PESECTHEADR = rnd(PEFILEHEADR, PESECTALIGN);
 	nextsectoff = PESECTHEADR;
 	nextfileoff = PEFILEHEADR;
+
+	// some mingw libs depend on this symbol, for example, FindPESectionByName
+	xdefine("__image_base__", SDATA, PEBASE);
 }
 
 static void

src/run.bat

@@ -64,11 +64,10 @@ echo.
 
 :: cgo tests
 if x%CGO_ENABLED% == x0 goto nocgo
-:: TODO(brainman) disabled, because it is broken on go builder - http://golang.org/issue/4063
-::echo # ..\misc\cgo\life
-::go run %GOROOT%\test\run.go - ..\misc\cgo\life
-::if errorlevel 1 goto fail
-::echo.
+echo # ..\misc\cgo\life
+go run %GOROOT%\test\run.go - ..\misc\cgo\life
+if errorlevel 1 goto fail
+echo.
 
 echo # ..\misc\cgo\stdio
 go run %GOROOT%\test\run.go - ..\misc\cgo\stdio