Fix missing include on musl, as strcmp is not transitively included
Remove arg-less declaration for non-glibc case: we have POSIX here,
getopt has same prototype in glibc and in musl
https://bugs.gentoo.org/934059
https://bugs.gentoo.org/944111
--- a/getopt.c
+++ b/getopt.c
@@ -43,6 +43,7 @@
 #endif
 
 #include <stdio.h>
+#include <string.h>
 
 /* Comment out all this code if we are using the GNU C Library, and are not
    actually compiling the library itself.  This code is part of the GNU C
--- a/getopt.h
+++ b/getopt.h
@@ -99,14 +99,12 @@
 #define optional_argument	2
 
 #if defined (__STDC__) && __STDC__
-#ifdef __GNU_LIBRARY__
 /* Many other libraries have conflicting prototypes for getopt, with
    differences in the consts, in stdlib.h.  To avoid compilation
    errors, only prototype getopt for the GNU C library.  */
+/* But in Gentoo we have glibc and musl, and they have same POSIX
+   definition */
 extern int getopt (int argc, char *const *argv, const char *shortopts);
-#else /* not __GNU_LIBRARY__ */
-extern int getopt ();
-#endif /* __GNU_LIBRARY__ */
 extern int getopt_long (int argc, char *const *argv, const char *shortopts,
 		        const struct option *longopts, int *longind);
 extern int getopt_long_only (int argc, char *const *argv,