musl is always ELFv2, no matter endianness.

--- mednafen/src/snes/src/lib/libco/ppc.c.old	2019-01-28 06:52:37.000000000 +0000
+++ mednafen/src/snes/src/lib/libco/ppc.c	2019-03-25 03:42:05.330000000 +0000
@@ -40,7 +40,7 @@
 /* Whether function calls are indirect through a descriptor,
 or are directly to function */
 #ifndef LIBCO_PPCDESC
-	#if !_CALL_SYSV && (_CALL_AIX || _CALL_AIXDESC || LIBCO_PPC64)
+	#if !_CALL_SYSV && (_CALL_AIX || _CALL_AIXDESC || (LIBCO_PPC64 && _CALL_ELF == 1))
 		#define LIBCO_PPCDESC 1
 	#endif
 #endif