cmd: add -maix32 to gcc calls for aix/ppc

As gcc might now be compiled in 64bit, -maix32 must always be added
to ensure that created objects will be 32bit.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/250778

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-aac2b382839154d74eeef160522c0a5c1ea8aadf
+9aed2d2c5e9c69aa530bf09d72d33c66e497d720
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/cmd/cgo/gcc.go

@@ -1573,6 +1573,10 @@ func (p *Package) gccMachine() []string {
 		if goos == "aix" {
 			return []string{"-maix64"}
 		}
+	case "ppc":
+		if goos == "aix" {
+			return []string{"-maix32"}
+		}
 	}
 	return nil
 }
@@ -1615,7 +1619,6 @@ func (p *Package) gccCmd() []string {
 	c = append(c, p.GccOptions...)
 	c = append(c, p.gccMachine()...)
 	if goos == "aix" {
-		c = append(c, "-maix64")
 		c = append(c, "-mcmodel=large")
 	}
 	c = append(c, "-") //read input from standard input

libgo/go/cmd/go/internal/work/exec.go

@@ -2503,6 +2503,10 @@ func (b *Builder) gccArchArgs() []string {
 		if cfg.Goos == "aix" {
 			return []string{"-maix64"}
 		}
+	case "ppc":
+		if cfg.Goos == "aix" {
+			return []string{"-maix32"}
+		}
 	}
 	return nil
 }