Check out llvm sources using the new llvm git monorepo

This updates compiler-rt, libunwind, libcxxabi and libcxx to a newer
version, matching the compiler.

This will be the official, canonical repo in the future.

For the non-dev Dockerfile build, this means that all the llvm based
subprojects need to be built in one RUN to avoid storing the llvm
checkout in the docker layers.

build-llvm.sh

@@ -31,46 +31,21 @@ PREFIX="$(cd "$PREFIX" && pwd)"
 : ${CORES:=$(sysctl -n hw.ncpu 2>/dev/null)}
 : ${CORES:=4}
 
-if [ ! -d llvm ]; then
+if [ ! -d llvm-project ]; then
     # When cloning master and checking out a pinned old hash, we can't use --depth=1.
-    git clone -b master https://github.com/llvm-mirror/llvm.git
-    cd llvm/tools
-    git clone -b master https://github.com/llvm-mirror/clang.git
-    git clone -b master https://github.com/llvm-mirror/lld.git
-    cd ..
-    set +e
-    # Do the git-svn rebase to populate git-svn information, to make
-    # "clang --version" produce SVN based version numbers.
-    # This is optional - don't error out here if git-svn is unavailable.
-    git svn init https://llvm.org/svn/llvm-project/llvm/trunk
-    git config svn-remote.svn.fetch :refs/remotes/origin/master
-    git svn rebase -l
-    cd tools/clang
-    git svn init https://llvm.org/svn/llvm-project/cfe/trunk
-    git config svn-remote.svn.fetch :refs/remotes/origin/master
-    git svn rebase -l
-    cd ../lld
-    git svn init https://llvm.org/svn/llvm-project/lld/trunk
-    git config svn-remote.svn.fetch :refs/remotes/origin/master
-    git svn rebase -l
-    cd ../../..
-    set -e
+    git clone -b master https://github.com/llvm/llvm-project.git
     CHECKOUT=1
 fi
 
 if [ -n "$SYNC" ] || [ -n "$CHECKOUT" ]; then
-    cd llvm
+    cd llvm-project
     [ -z "$SYNC" ] || git fetch
-    git checkout 66495492c0af53c4597cace26c50f0dce44033fc
-    cd tools/clang
-    [ -z "$SYNC" ] || git fetch
-    git checkout 6fddf7789c74ae74d695dd571024915ad319db1b
-    cd ../lld
-    [ -z "$SYNC" ] || git fetch
-    git checkout 1e90cb9d20d4fcdb5d1448853370e969035d8014
-    cd ../../..
+    git checkout e698958ad8031e0f17202e06f5de53989852bb66
+    cd ..
 fi
 
+[ -z "$CHECKOUT_ONLY" ] || exit 0
+
 if [ -n "$(which ninja)" ]; then
     CMAKE_GENERATOR="Ninja"
     NINJA=1
@@ -86,12 +61,12 @@ fi
 
 if [ -n "$HOST" ]; then
     find_native_tools() {
-        if [ -d llvm/build/bin ]; then
-            echo $(pwd)/llvm/build/bin
-        elif [ -d llvm/build-asserts/bin ]; then
-            echo $(pwd)/llvm/build-asserts/bin
-        elif [ -d llvm/build-noasserts/bin ]; then
-            echo $(pwd)/llvm/build-noasserts/bin
+        if [ -d llvm-project/llvm/build/bin ]; then
+            echo $(pwd)/llvm-project/llvm/build/bin
+        elif [ -d llvm-project/llvm/build-asserts/bin ]; then
+            echo $(pwd)/llvm-project/llvm/build-asserts/bin
+        elif [ -d llvm-project/llvm/build-noasserts/bin ]; then
+            echo $(pwd)/llvm-project/llvm/build-noasserts/bin
         elif [ -n "$(which llvm-tblgen)" ]; then
             echo $(dirname $(which llvm-tblgen))
         fi
@@ -130,7 +105,7 @@ if [ -n "$FULL_LLVM" ]; then
     TOOLCHAIN_ONLY=OFF
 fi
 
-cd llvm
+cd llvm-project/llvm
 mkdir -p $BUILDDIR
 cd $BUILDDIR
 cmake \
@@ -138,6 +113,7 @@ cmake \
     -DCMAKE_INSTALL_PREFIX="$PREFIX" \
     -DCMAKE_BUILD_TYPE=Release \
     -DLLVM_ENABLE_ASSERTIONS=$ASSERTS \
+    -DLLVM_ENABLE_PROJECTS="clang;lld" \
     -DLLVM_TARGETS_TO_BUILD="ARM;AArch64;X86" \
     -DLLVM_INSTALL_TOOLCHAIN_ONLY=$TOOLCHAIN_ONLY \
     -DLLVM_TOOLCHAIN_TOOLS="llvm-ar;llvm-ranlib;llvm-objdump;llvm-rc;llvm-cvtres;llvm-nm;llvm-strings;llvm-readobj;llvm-dlltool;llvm-pdbutil;llvm-objcopy;llvm-strip;llvm-cov;llvm-profdata;llvm-addr2line" \