security/heimdal-devel: Convert to new USES=llvm

Replace BUILD_DEPENDS with the new USES=llvm infrastructure.

security/heimdal-devel/Makefile

@@ -25,8 +25,8 @@ USE_LDCONFIG=	${GSSAPILIBDIR}
 
 # Needs clang-format which is only provided by the port.
 # Else asm1_fails resulting in a command not found error.
-BUILD_DEPENDS=	clang${LLVM_DEFAULT}:devel/llvm${LLVM_DEFAULT} \
-		p5-JSON>0:converters/p5-JSON
+USES+=		llvm
+BUILD_DEPENDS=	p5-JSON>0:converters/p5-JSON
 
 GNU_CONFIGURE=	yes
 CONFIGURE_ENV=	ac_cv_header_fnmatch_h=yes \