fontconfig: fix build with SDK producing -dD style output

fontconfig: fix build with SDK producing -dD style output

Some SDK/host GCC configurations, when meson invokes cc.preprocess() to
expand fcobjshash.gperf.h, produce output that includes predefined macro
dumps (e.g. #define __STDC__ 1) alongside linemarker lines. The upstream
cutout.py script, which strips CUT_OUT_BEGIN/END-delimited sections from
the preprocessed output before feeding it to gperf, passes these lines
through verbatim into fcobjshash.gperf.

gperf then copies them into the declarations section of fcobjshash.h.
When fcobjs.c includes fcobjshash.h, the compiler encounters #define
redefinitions and stray # tokens, causing a build failure.

Fix cutout.py to skip any line starting with # (C preprocessor
linemarkers and predefined macro definitions) before writing to the
output gperf file.

Signed-off-by: Alexandru Ardelean <redacted>