Fix: fix sccache bug for dwo file generate

[zhouronghua]

When output dir changed, and -g -gsplit-dwarf is enabled,
because the object file have link to the dwo file (include directories),
the new object file should be gererated, but not old cached object.
In this patch, we add a new precompile macro, for example, "-D_gsplit_dwarf_path=foo.dwo", to force sccache to generate new object file depend on the output directories.

we can check if it work by this case:
case:

echo "int test(){}" > test.cc
mkdir o1 o2
sccache g++ -c -g -gsplit-dwarf test.cc -o o1/test.o
sccache g++ -c -g -gsplit-dwarf test.cc -o o2/test.o
strings o2/test.o |grep o2/test.dwo

The new o2/test.o should contains new link to o2/test.dwo, but not cached o1/test.dwo

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 40.67%. Comparing base (0cc0c62) to head (4a14637).
Report is 81 commits behind head on main.

Files with missing lines	Patch %	Lines
src/compiler/gcc.rs	66.66%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2271      +/-   ##
==========================================
+ Coverage   30.91%   40.67%   +9.76%     
==========================================
  Files          53       54       +1     
  Lines       20112    20758     +646     
  Branches     9755     9651     -104     
==========================================
+ Hits         6217     8443    +2226     
- Misses       7922     8155     +233     
+ Partials     5973     4160    -1813     

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[sylvestre]

Could you please add a test to make sure we don't regress in the future? thanks

[zhouronghua]

"test_parse_arguments_split_dwarf" this case has been modified to make it work all the time

[sylvestre]

this isn't enough. I would like to see a test reproducing:

echo "int test(){}" > test.cc
mkdir o1 o2
sccache g++ -c -g -gsplit-dwarf test.cc -o o1/test.o
sccache g++ -c -g -gsplit-dwarf test.cc -o o2/test.o
strings o2/test.o |grep o2/test.dwo

also, you didn't updated the clang.rs file, is that expected ?

[zhouronghua]

ok, I will add another test for it, but it need time.

parse_arguments in clang.rs will call parse_arguments in gcc.rs, so no need to change them all.

[sylvestre]

see https://github.com/mozilla/sccache/blob/main/tests/system.rs for example