std.os.linux: block all signals in raise

lib/std/posix.zig

@@ -720,9 +720,19 @@ pub fn raise(sig: u8) RaiseError!void {
     }
 
     if (native_os == .linux) {
+        // https://git.musl-libc.org/cgit/musl/commit/?id=0bed7e0acfd34e3fb63ca0e4d99b7592571355a9
+        //
+        // Unlike musl, libc-less Zig std does not have any internal signals for implementation purposes, so we
+        // need to block all signals on the assumption that any of them could potentially fork() in a handler.
+        var set: sigset_t = undefined;
+        sigprocmask(SIG.BLOCK, &linux.all_mask, &set);
+
         const tid = linux.gettid();
         const rc = linux.tkill(tid, sig);
 
+        // restore signal mask
+        sigprocmask(SIG.SETMASK, &set, null);
+
         switch (errno(rc)) {
             .SUCCESS => return,
             else => |err| return unexpectedErrno(err),