all: include picolibc for bare metal targets

This is necessary for better CGo support on bare metal. Existing
libraries expect to be able to include parts of libc and expect to be
able to link to those symbols.

Because with this all targets have a working libc, it is now possible to
add tests to check that a libc in fact works basically.

Not all parts of picolibc are included, such as the math or stdio parts.
These should be added later, when needed.

This commit also avoids the need for the custom memcpy/memset/memcmp
symbols that are sometimes emitted by LLVM. The C library will take care
of that.

1 files changed, 17 insertions, 2 deletions

diff --git a/main.go b/main.go
index c21b1377b..d4361d13b 100644
--- a/main.go
+++ b/main.go
@@ -786,7 +786,7 @@ func main() {
 		}
 		err := Build(pkgName, *outpath, options)
 		handleCompilerError(err)
-	case "build-builtins":
+	case "build-library":
 		// Note: this command is only meant to be used while making a release!
 		if *outpath == "" {
 			fmt.Fprintln(os.Stderr, "No output filename supplied (-o).")
@@ -796,7 +796,22 @@ func main() {
 		if *target == "" {
 			fmt.Fprintln(os.Stderr, "No target (-target).")
 		}
-		path, err := builder.CompilerRT.Load(*target)
+		if flag.NArg() != 1 {
+			fmt.Fprintf(os.Stderr, "Build-library only accepts exactly one library name as argument, %d given\n", flag.NArg())
+			usage()
+			os.Exit(1)
+		}
+		var lib *builder.Library
+		switch name := flag.Arg(0); name {
+		case "compiler-rt":
+			lib = &builder.CompilerRT
+		case "picolibc":
+			lib = &builder.Picolibc
+		default:
+			fmt.Fprintf(os.Stderr, "Unknown library: %s\n", name)
+			os.Exit(1)
+		}
+		path, err := lib.Load(*target)
 		handleCompilerError(err)
 		copyFile(path, *outpath)
 	case "flash", "gdb":