OpenSSL @OS X: choose correct build target

Change-Id: I58f3cc12f2fa177c26608d372f99c086503a13a5
Reviewed-on: https://gerrit.libreoffice.org/8205
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>

external/openssl/ExternalProject_openssl.mk

@@ -49,7 +49,9 @@ OPENSSL_PLATFORM := \
           )\
         ,\
           $(if $(filter MACOSX,$(OS)),\
-            $(if $(filter INTEL,$(CPUNAME)),darwin-i386-cc,darwin64-x86_64-cc)\
+            $(if $(filter POWERPC,$(CPUNAME)),darwin-ppc-cc)\
+            $(if $(filter INTEL,$(CPUNAME)),darwin-i386-cc)\
+            $(if $(filter X86_64,$(CPUNAME)),darwin64-x86_64-cc)\
           )\
         )\
       )\