Update LLVM build system for 249b40b558955afe5ac2b549edcf2d7f859c8cc9

This enables the use of modules for a significant build performance gain
when building with clang as host compiler or when using

Update LLVM build system for 249b40b558955afe5ac2b549edcf2d7f859c8cc9

This enables the use of modules for a significant build performance gain
when building with clang as host compiler or when using HAVE_LLVM=yes.
Switch libc++ to using the copy from the mono-repo.

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Revert last. It was objected to pre-commit, there is no actual error
analysis or report and there is existing logic supposed to handle this.

Disable HAVE_TERMINFO and HAVE_TERMIOS_H for ./build.sh tools build

These headers enable optional features and are not portable to all host
Operating Systems.

Speculative fix for certain Linux dist

Disable HAVE_TERMINFO and HAVE_TERMIOS_H for ./build.sh tools build

These headers enable optional features and are not portable to all host
Operating Systems.

Speculative fix for certain Linux distributions.

show more ...

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)