java/openjdk11: fix build on powerpc64*

Go back to using LLVM 12, bin/java built with LLVM 13 crashes with:
* For target jdk__packages_attribute.done:

 A fatal error has been detected by the Java Runtime Environment:

  SIGILL (0x4) at pc=0x0000000802e3d438, pid=28756, tid=149399

 JRE version:  (11.0.16+8) (build )
 Java VM: OpenJDK 64-Bit Server VM (11.0.16+8-1, mixed mode, tiered, compressed oops, serial gc, bsd-ppc64)
 Problematic frame:
 V  [libjvm.so+0xe3d438]  JVM_RaiseSignal+0x446bcc

java/openjdk11/Makefile

@@ -141,6 +141,12 @@ CONFIGURE_ARGS+=	--with-extra-ldflags="-Wl,-rpath=${LOCALBASE}/lib/gcc${GCC_DEFA
 			--with-extra-cxxflags="-Wl,-rpath=${LOCALBASE}/lib/gcc${GCC_DEFAULT}"
 .else
 MAKE_ENV+=	USE_CLANG=true
+.if ${COMPILER_VERSION} >= 130 && ${ARCH:Mpowerpc64*}
+LLVM_VER=	12
+BUILD_DEPENDS+=	clang${LLVM_VER}:devel/llvm${LLVM_VER}
+CC=		${LOCALBASE}/bin/clang${LLVM_VER}
+CXX=		${LOCALBASE}/bin/clang++${LLVM_VER}
+.endif
 .endif
 
 .if ${ARCH} == aarch64 || ${ARCH:Marmv*} || ${ARCH:Mpowerpc64*}