build clang from tar.xz sources on centos 7

build.bash

yum -y install centos-release-scl which devtoolset-7-gcc* libxml2-devel zlib-devel
scl enable devtoolset-7 bash
gcc --version

cat >/tmp/llvm.sh <<'EOL'
#LLVMDIR="/usr/local/src/llvm"
#build in ramdisk if it's >= 8GB
LLVMDIR="/run/llvm"
LLVMVER="8.0.0"
TEST_CC="/opt/rh/devtoolset-7/root/usr/bin/cc"
TEST_GCC="/opt/rh/devtoolset-7/root/usr/bin/gcc"

rm -rf "$LLVMDIR/build"
ls "$LLVMDIR" || mkdir -p "$LLVMDIR"

cd "$LLVMDIR"
wget "http://releases.llvm.org/$LLVMVER/llvm-$LLVMVER.src.tar.xz"
tar xf "llvm-$LLVMVER.src.tar.xz" --no-same-owner

cd "llvm-$LLVMVER.src/projects"

wget "http://releases.llvm.org/$LLVMVER/compiler-rt-$LLVMVER.src.tar.xz"
tar xf "compiler-rt-$LLVMVER.src.tar.xz" --no-same-owner
mv "compiler-rt-$LLVMVER.src" compiler-rt

wget "http://releases.llvm.org/$LLVMVER/libcxx-$LLVMVER.src.tar.xz"
tar xf "libcxx-$LLVMVER.src.tar.xz" --no-same-owner
mv "libcxx-$LLVMVER.src" libcxx

wget "http://releases.llvm.org/$LLVMVER/libcxxabi-$LLVMVER.src.tar.xz"
tar xf "libcxxabi-$LLVMVER.src.tar.xz" --no-same-owner
mv "libcxxabi-$LLVMVER.src" libcxxabi

wget "http://releases.llvm.org/$LLVMVER/libunwind-$LLVMVER.src.tar.xz"
tar xf "libunwind-$LLVMVER.src.tar.xz" --no-same-owner
mv "libunwind-$LLVMVER.src" libunwind

rm -f *.src.tar.xz

cd "$LLVMDIR"/llvm-$LLVMVER.src/tools

wget "http://releases.llvm.org/$LLVMVER/cfe-$LLVMVER.src.tar.xz"
tar xf "cfe-$LLVMVER.src.tar.xz" --no-same-owner
mv "cfe-$LLVMVER.src" clang

wget "http://releases.llvm.org/$LLVMVER/lld-$LLVMVER.src.tar.xz"
tar xf "lld-$LLVMVER.src.tar.xz" --no-same-owner
mv "lld-$LLVMVER.src" lld

wget "http://releases.llvm.org/$LLVMVER/lldb-$LLVMVER.src.tar.xz"
tar xf "lldb-$LLVMVER.src.tar.xz" --no-same-owner
mv "lldb-$LLVMVER.src" lldb

rm -f *.src.tar.xz

mkdir "$LLVMDIR/build" && cd "$LLVMDIR/build"

cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr/local -DLLVM_LIBDIR_SUFFIX=64 -DLLVM_ENABLE_EH=ON -DLLVM_ENABLE_RTTI=ON -DLLDB_TEST_C_COMPILER="$TEST_CC" -DLLDB_TEST_CXX_COMPILER="$TEST_GCC" ../llvm-$LLVMVER.src
#cmake --build .
cmake --build . --target install -- -j $(nproc)
#cmake -DCMAKE_INSTALL_PREFIX=/usr/local/src/clang/1 -P cmake_install.cmake
EOL
bash /tmp/llvm.sh >> /tmp/llvm.log 2>&1