This is the first patch from the set of patches extracted from D70709.
That refactoring moves NonRelocatableStringpool into common CodeGen folder.
So that NonRelocatableStringpool could be used not only inside dsymutil.
Testing results:
check-all - passed.
golden/new comparison:
golden-dsymutil/dsymutil build-Debug/bin/clang
md5 -r build-Debug/bin/clang.dSYM/Contents/Resources/DWARF/clang
a31430a6a2fbbd81fbed88888c769213 build-Debug/bin/clang.dSYM/Contents/Resources/DWARF/clang
new-dsymutil/dsymutil build-Debug/bin/clang
md5 -r build-Debug/bin/clang.dSYM/Contents/Resources/DWARF/clang
a31430a6a2fbbd81fbed88888c769213 build-Debug/bin/clang.dSYM/Contents/Resources/DWARF/clang