Build build scripts for sysroot using cg_llvm

There is not yet a cg_clif sysroot available when building the sysroot itself

Author: bjorn3

build_sysroot/build_sysroot.sh

@@ -14,8 +14,13 @@ popd >/dev/null
 rm -r target/*/{debug,release}/{build,deps,examples,libsysroot*,native} 2>/dev/null || true
 rm -r sysroot/ 2>/dev/null || true
 
+# Use rustc with cg_clif as hotpluggable backend instead of the custom cg_clif driver so that
+# build scripts are still compiled using cg_llvm.
+export RUSTC=rustc
+export RUSTFLAGS=$RUSTFLAGS" -Ztrim-diagnostic-paths=no -Zcodegen-backend=$(pwd)/../target/"$CHANNEL"/librustc_codegen_cranelift."$dylib_ext" --sysroot $(pwd)/sysroot"
+
 # Build libs
-export RUSTFLAGS="$RUSTFLAGS -Z force-unstable-if-unmarked"
+export RUSTFLAGS="$RUSTFLAGS -Zforce-unstable-if-unmarked -Cpanic=abort"
 if [[ "$1" == "--release" ]]; then
     sysroot_channel='release'
     # FIXME Enable incremental again once rust-lang/rust#74946 is fixed