sci-physics/root: disable cling -isystem injection.

This fixes the ACLiC failure on Prefix.

  We use SYSROOT to guide llvm in ROOT to locate headers and libraries
  at build time.  Such feature is not to be used at runtime.

  The patch has no effect to usual Gentoo, therefore applying it
  unconditionally.

Closes: https://bugs.gentoo.org/653124
Package-Manager: Portage-2.3.28, Repoman-2.3.9

sci-physics/root/files/root-6.12.06_cling-runtime-sysroot.patch

@@ -0,0 +1,22 @@
+On Prefix, we have specified SYSROOT for llvm at build time.  But we
+  do not need sysroot at runtime as we are not crosscompiling.
+
+This patch disable the sysroot feature for cling, so that ACLiC can
+work on Prefix.
+
+Index: root-6.12.06/interpreter/cling/lib/Utils/Paths.cpp
+===================================================================
+--- root-6.12.06.orig/interpreter/cling/lib/Utils/Paths.cpp
++++ root-6.12.06/interpreter/cling/lib/Utils/Paths.cpp
+@@ -57,11 +57,6 @@ using namespace clang;
+ void CopyIncludePaths(const clang::HeaderSearchOptions& Opts,
+                       llvm::SmallVectorImpl<std::string>& incpaths,
+                       bool withSystem, bool withFlags) {
+-  if (withFlags && Opts.Sysroot != "/") {
+-    incpaths.push_back("-isysroot");
+-    incpaths.push_back(Opts.Sysroot);
+-  }
+-
+   /// User specified include entries.
+   for (unsigned i = 0, e = Opts.UserEntries.size(); i != e; ++i) {
+     const HeaderSearchOptions::Entry &E = Opts.UserEntries[i];

sci-physics/root/root-6.12.06-r1.ebuild

@@ -134,6 +134,7 @@ src_prepare() {
 	cmake-utils_src_prepare
 
 	hprefixify build/CMakeLists.txt core/clingutils/CMakeLists.txt
+	eapply "${FILESDIR}"/${PN}-6.12.06_cling-runtime-sysroot.patch
 
 	# CSS should use local images
 	sed -i -e 's,http://.*/,,' etc/html/ROOT.css || die "html sed failed"