[Bug other/70268] add option -ffile-prefix-map to map one directory name (old) to another (new) in __FILE__, __BASE_FILE__and __builtin_FILE()

[hongxu.jia at windriver dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70268

--- Comment #1 from hongxu jia <hongxu.jia at windriver dot com> ---
So I suggest gcc could provide a option '-ffile-prefix-map=<old>=<new>'
to map <old> directory in __FILE__ and replace it with <new> directory.

It is similar to '-fdebug-prefix-map=<old>=<new>', but the latter is used
for DWARF, and the newly added option only works on '__FILE__', '__BASE_FILE__'
and '__builtin_FILE()'

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5. Compile C source file with '-ffile-prefix-map'
$ gcc ./test.c -ffile-prefix-map=/usr/include= -o test

4. Execute and the header file is not pull path.
$ ./test 
__FILE__ ./test.c
__FILE__ /test.h
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