Index: head/math/openlibm/Makefile
===================================================================
--- head/math/openlibm/Makefile
+++ head/math/openlibm/Makefile
@@ -17,9 +17,8 @@
 BROKEN_armv7=		fails to compile: a parameter list without types is only allowed in a function definition
 BROKEN_mips=		fails to compile: No rule to make target mips/Make.files
 BROKEN_mips64=		fails to compile: No rule to make target mips64/Make.files
-BROKEN_powerpc64=	fails to build: gmake: clang: Command not found
 
-USES=	gmake
+USES=	compiler:c11 gmake
 USE_GITHUB=	yes
 GH_ACCOUNT=	JuliaMath
 GH_PROJECT=	openlibm
@@ -28,8 +27,16 @@
 
 .include <bsd.port.pre.mk>
 
-MAKE_ENV+=	prefix=${PREFIX}
+MAKE_ENV+=	prefix=${PREFIX} ${MAKE_ENV_${CHOSEN_COMPILER_TYPE}}
+MAKE_ENV_gcc=	USEGCC=1 USECLANG=0
+MAKE_ENV_clang=	USEGCC=0 USECLANG=1
 
 TEST_TARGET=	check
 
+post-patch:
+	${REINPLACE_CMD} -e 's/USEGCC =/USEGCC ?=/g' \
+		-e 's/USECLANG =/USECLANG ?=/g' \
+		-e '/TOOLPREFIX)gcc/s/$$/${GCC_DEFAULT}/g' \
+		${WRKSRC}/Make.inc
+		
 .include <bsd.port.post.mk>