llvm tool build: fix warning

-std=c++14 is for HOST_CXXFLAGS not HOST_CPPFLAGS.

Fixes: cc1: warning: command-line option '-std=c++14' is valid for C++/ObjC++ but not for C

adapt to ${CC_WNO_STRINGOP_OVERFLOW}

Use ${CC_WNO_STRINGOP_OVERFLOW} instead of
the older style more complex expressions.

Remove workarounds if they were only for gcc < 10.

When MKDEBUG is use, build LLVM with -g1 to significantly reduce debug
information. This still includes types and line tables, but skips e.g.
local variables and inline tracking.

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.

branches: 1.4.4;
Use -fno-strict-aliasing unconditionally for the cross compiler.

Use a big hammer and disabling strict aliasing for the tools build or
when using GCC.

For gcc < 9 disable stringop-overflow warnings - they are broken.

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)

When MKDEBUG is use, build LLVM with -g1 to significantly reduce debug
information. This still includes types and line tables, but skips e.g.
local variables and inline tracking.

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.

branches: 1.4.4;
Use -fno-strict-aliasing unconditionally for the cross compiler.

Use a big hammer and disabling strict aliasing for the tools build or
when using GCC.

For gcc < 9 disable stringop-overflow warnings - they are broken.

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)

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.

Use -fno-strict-aliasing unconditionally for the cross compiler.

Use a big hammer and disabling strict aliasing for the tools build or
when using GCC.

For gcc < 9 disable stringop-overflow warnings - they are broken.

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)

Use -fno-strict-aliasing unconditionally for the cross compiler.

Use a big hammer and disabling strict aliasing for the tools build or
when using GCC.

For gcc < 9 disable stringop-overflow warnings - they are broken.

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)

Use a big hammer and disabling strict aliasing for the tools build or
when using GCC.

For gcc < 9 disable stringop-overflow warnings - they are broken.

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)

For gcc < 9 disable stringop-overflow warnings - they are broken.

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)

Update LLVM to 10.0.0git (01f3a59fb3e2542fce74c768718f594d0debd0da)