llvm8, llvm6.0: add metapackages to force removal

This will allow old systems to upgrade. Right now we have a problem
that old mesa used to depend on libllvm8, which will block upgrading
as it depends on libffi which in the meantime did a soname bump. So
you will have llvm8 blocking upgrade because of soname conflict,
which cannot upgrade as it's already gone, which prevents upgrade
of everything else.

srcpkgs/libllvm6.0

@@ -0,0 +1 @@
+llvm6.0

srcpkgs/libllvm8

@@ -0,0 +1 @@
+llvm8

srcpkgs/llvm6.0/INSTALL.msg

@@ -0,0 +1 @@
+llvm6.0 is no longer provided by Void Linux

srcpkgs/llvm6.0/template

@@ -0,0 +1,14 @@
+# Template file for 'llvm6.0'
+pkgname=llvm6.0
+version=6.0.1
+revision=7
+archs=noarch
+build_style=meta
+short_desc="Low Level Virtual Machine (6.0.x series) (removed package)"
+maintainer="Orphaned <orphan@voidlinux.org>"
+license="NCSA"
+homepage="https://www.llvm.org"
+
+libllvm6.0_package() {
+	short_desc+=" - runtime library"
+}

srcpkgs/llvm8/INSTALL.msg

@@ -0,0 +1 @@
+llvm8 is no longer provided by Void Linux

srcpkgs/llvm8/template

@@ -0,0 +1,14 @@
+# Template file for 'llvm8'
+pkgname=llvm8
+version=8.0.1
+revision=4
+archs=noarch
+build_style=meta
+short_desc="Low Level Virtual Machine (removed package)"
+maintainer="Enno Boland <gottox@voidlinux.org>"
+license="metapackage"
+homepage="https://www.llvm.org"
+
+libllvm8_package() {
+	short_desc+=" - runtime library"
+}