fopen_internal: do not resolve cdromL by default

This avoids calling malloc(3) and thus allowing the linker to remove
the heap implementation from memory.c via --gc-sections.

libpsx/src/libc.c

@@ -11,6 +11,7 @@
 
 #include <psx.h>
 #include <stdio.h>
+#include <stddef.h>
 #include <string.h>
 #include <stdlib.h>
 #include <strings.h>
@@ -164,12 +165,16 @@ static FILE *fopen_internal(const char *path, const char *mode, FILE *f)
 
 	if(strncmp(path, "cdromL:", 7) == 0)
 	{
+#ifdef PSXSDK_CDROML_ENABLED
 		s = malloc(1024);
 
 		if(libc_get_transtbl_fname(path+7, s, 1024) == 0)
 			return NULL;
 
 		fd = open(s, fmode_to_desmode(mode));
+#else
+		return NULL;
+#endif
 	}
 	else
 		fd = open(path, fmode_to_desmode(mode));