Clang build is extremely slow and hangs up in the

Question

I am getting started with writing my own clang tools. These are the steps I have followed so far:

1. Checked out llvm 7.0 release build
2. Checked out clang 7.0 release build

3. Built clang and llvm using ninja with following flags (It was hanging up on me constantly without these)

   -DLLVM_USE_LINKER=gold -DLLVM_PARALLEL_LINK_JOBS=1 -DLLVM_LINK_LLVM_DYLIB=true -DLLVM_USE_SPLIT_DWARF=ON -DBUILD_SHARED_LIBS=ON

4. Installed clang

Now I want to set clang as it's own compiler. So I have set these flags in config file using 'ccmake ../llvm'. I'm not sure if that was the right thing to do though? Now that I try to build clang it says linker detected is GNU ld. How can I reset my config file and actually change the linker so it will be faster? I have 8GB RAM.

Secondly, would I have to build clang again and again every time I write a tool? As in would it take 3-4 hours every single time?

Update As suggested by sandthorn in comments I limited parallel jobs to 1 by using ninja -j 1. However, the build failed again with following error:

[3840/4138] Linking CXX shared library lib/libLTO.so.7
FAILED: lib/libLTO.so.7 
: && /usr/bin/c++ -fPIC -fPIC -fvisibility-inlines-hidden -Werror=date-time -std=c++11 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wno-maybe-uninitialized -Wdelete-non-virtual-dtor -Wno-comment -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -Wl,-z,defs -Wl,-z,nodelete -fuse-ld=gold   -Wl,-O3 -Wl,--gc-sections  -Wl,--version-script,/home/tehreem/clang-llvm/build/tools/lto/LTO.exports -shared -Wl,-soname,libLTO.so.7 -o lib/libLTO.so.7 tools/lto/CMakeFiles/LTO.dir/LTODisassembler.cpp.o tools/lto/CMakeFiles/LTO.dir/lto.cpp.o  -Wl,-rpath,"\$ORIGIN/../lib" lib/libLLVM-7.so && :

And after this there are about a 100 other undefined reference errors.