builder: add some more musl support

This should add just enough for the Boehm GC, which uses printf in some
cases and therefore needs somewhat more complete libc support.

builder/musl.go

@@ -113,23 +113,30 @@ var Musl = Library{
 	librarySources: func(target string) ([]string, error) {
 		arch := compileopts.MuslArchitecture(target)
 		globs := []string{
+			"ctype/*.c",
 			"env/*.c",
 			"errno/*.c",
 			"exit/*.c",
+			"fcntl/*.c",
 			"internal/defsysinfo.c",
+			"internal/intscan.c",
 			"internal/libc.c",
+			"internal/shgetc.c",
 			"internal/syscall_ret.c",
 			"internal/vdso.c",
 			"legacy/*.c",
 			"locale/*.c",
 			"linux/*.c",
+			"locale/*.c",
 			"malloc/*.c",
 			"malloc/mallocng/*.c",
 			"mman/*.c",
 			"math/*.c",
 			"multibyte/*.c",
+			"sched/*.c",
 			"signal/*.c",
 			"stdio/*.c",
+			"stdlib/*.c",
 			"string/*.c",
 			"thread/" + arch + "/*.s",
 			"thread/*.c",