[ccache] gcc -pipe support

[rafal bursig]

Hi All,

Current pre-processor output is stored in tmp.i/ii file on disk and read
again by ccache (md4 calc.) and compiler (as input).

This patch add "pipe" support to ccache. If user add "-pipe" option to
compilrer args. then ccache use pipes (unnamed) to calc. md4 sum and tmp
fifo file as compiler input.

Patch increase memory usage becouse i/ii data is stored in memory before
using by compiler. (This not happend when user use CCACHE_CPP2 env.
flag.)

In theory this fix can inprove speed of ccache becouse md4 calculation
is make parallel with pre-compiler but I don't test this aspect. (if
someone could make some tests I will be happy)

Rafal Bursig

PS. for any answers please CC me.



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