ww build: honor Go output permission modes

test/package/umaskexec.c

@@ -0,0 +1,27 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+int
+main(int argc, char **argv)
+{
+	char *end;
+	unsigned long mask;
+
+	if (argc < 3) {
+		fputs("usage: package-umaskexec MASK PROGRAM [ARG ...]\n", stderr);
+		return 2;
+	}
+	errno = 0;
+	mask = strtoul(argv[1], &end, 8);
+	if (errno != 0 || end == argv[1] || *end != '\0' || mask > 0777) {
+		fputs("package-umaskexec: invalid mask\n", stderr);
+		return 2;
+	}
+	umask((mode_t)mask);
+	execv(argv[2], &argv[2]);
+	fputs("package-umaskexec: exec failed\n", stderr);
+	return 127;
+}