Disable the PCH valid check to save a lot of compiling time.
Disable the PCH valid check to save a lot of compiling time.

In clang, The PCH file will be used as an AST source, so
the check is strict. The macro define is also checked,
and if anything is different, the PCH is invalid and
the build processing will start from scratch.
Disable Clang's PCH valid check and do the compatible
check by ourself.

This patch do not solve the clang version problems.
Because the AST represent is an internal Clang's
data struct and may change between two clang versions.
So we will modify this issue later.

Signed-off-by: Junyan He <8f73a735c668918c9613b750d3a88ebf2489599f@linux.intel.com>
Reviewed-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>
Reviewed-by: "Song, Ruiling" <286a174c1339c6eff91abc41c3a1012c95030c95@intel.com>

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