util/amdfwtool: guard typedef aliases

Build tested on Ubuntu 18 LTS, FreeBSD.

Change-Id: Ida2c1f36aba7469d69dbb12ee6afce4a181bd6b7
Signed-off-by: Idwer Vollering <vidwer@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37766
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/amdfwtool/amdfwtool.c

@@ -110,10 +110,12 @@
  */
 #define PSP_COMBO 0
 
+#if defined(__GLIBC__)
 typedef unsigned long long int uint64_t;
 typedef unsigned int uint32_t;
 typedef unsigned char uint8_t;
 typedef unsigned short uint16_t;
+#endif
 
 /*
  * Creates the OSI Fletcher checksum. See 8473-1, Appendix C, section C.3.