devel/llvm-base: switch to init-all=zero

Zero bits of the stack the compiler can't prove are initialized before
use or escape by default.

Issue:		CTSRD-CHERI/cheribsd#2045

devel/llvm-base/Makefile

@@ -1,5 +1,5 @@
 PORTNAME=	llvm
-PORTVERSION=	5
+PORTVERSION=	6
 CATEGORIES=	devel lang
 MASTER_SITES=	# not applicable
 DISTFILES=	# not applicable

devel/llvm-base/files/wrapper.sh.in

@@ -91,6 +91,15 @@ esac
 # version in ${LOCALBASE}/bin to ensure LD_LIBRARY_PATH is correct.
 realtool=${LOCALBASE}/bin/${llvmtool}
 
+cflags=
+if [ "$CHERIBSD_VERSION" -gt 20230804 ]; then
+	cflags="-ftrivial-auto-var-init=zero"
+	# XXX: The -enable-... flag becomes a warning in clang 16 and is
+	# removed in llvm 18.  Remove this once llvm-cheri and llvm-morello
+	# no longer require it.
+	cflags="${cflags} -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang"
+fi
+
 # CheriBSD: assume that if we're on a CHERI architecture we want either
 # purecap or hybrid binaries.
 arch_cflags=
@@ -131,7 +140,7 @@ esac
 
 case $tool in
 cc|c++|cpp)
-	toolflags=$arch_cflags
+	toolflags="$cflags $arch_cflags"
 	;;
 ld|ld.lld)
 	# no flags should be required as ld can see what it's doing from