Additional options to selectively pass to gcc when compiling certain files. This option can be passed multiple times. Syntax: regex_filter@option_1, option_2,...,option_n. Where regex_filter stands for a list of include and exclude regular expression patterns (Also see --instrumentation_filter). option_1 to option_n stand for arbitrary command line options. If an option contains a comma it has to be quoted with a backslash. Options can contain @. Only the first @ is used to split the string. Example: -- per_file_copt=//foo/.*\.cc,-//foo/bar\.cc@-O0 adds the -O0 command line option to the gcc command line of all cc files in //foo/ except bar.cc.