[lmi] Error on line 20 of a file that doesn't exist?

[Greg Chicares]

Using cygwin on an msw-10 corporate laptop...by adding
  git reset --hard
to scripts before 'git checkout (as previously discussed) and, similarly,
  git submodule foreach 'git reset --hard'
we've managed to get 'install_wx.sh' past the git-checkout step. Notably,
this submodule is updated:

Submodule path 'src/png': checked out '3ffeff7877598d3236cc09a6d3f478073eb33f35'

[and I see "HEAD detached at 3ffeff787" on my own machine, where
everything works just fine, so that seems to be the right SHA1]

...as well as the others. The 'configure' step seems to run as expected.
Then compilation begins; several wxregex, wxzlib, and wxpng files
compile successfully, including 'wxpng_filter_neon_intrinsics.o' shown
below, but then 'wxpng_palette_neon_intrinsics.o' has a fatal error:

i686-w64-mingw32-gcc -c -o wxpng_filter_neon_intrinsics.o 
-D_FILE_OFFSET_BITS=64 
-I/opt/lmi/local/gcc_i686-w64-mingw32/wx-ad_hoc/lmi-gcc-8.1.0/lib/wx/include/i686-w64-mingw32-msw-unicode-3.1
 -I/srv/cache_for_lmi/vcs/wxWidgets/include -I/opt/lmi/local/include  -DNDEBUG 
-I/srv/cache_for_lmi/vcs/wxWidgets/src/zlib -DPNG_INTEL_SSE -mthreads -Wall 
-Wundef -O2 -fno-ms-extensions -fno-omit-frame-pointer -frounding-math    
-I/opt/lmi/local/include -fno-ms-extensions -fno-omit-frame-pointer 
-frounding-math 
/srv/cache_for_lmi/vcs/wxWidgets/src/png/arm/filter_neon_intrinsics.c
i686-w64-mingw32-gcc -c -o wxpng_palette_neon_intrinsics.o 
-D_FILE_OFFSET_BITS=64 
-I/opt/lmi/local/gcc_i686-w64-mingw32/wx-ad_hoc/lmi-gcc-8.1.0/lib/wx/include/i686-w64-mingw32-msw-unicode-3.1
 -I/srv/cache_for_lmi/vcs/wxWidgets/include -I/opt/lmi/local/include  -DNDEBUG 
-I/srv/cache_for_lmi/vcs/wxWidgets/src/zlib -DPNG_INTEL_SSE -mthreads -Wall 
-Wundef -O2 -fno-ms-extensions -fno-omit-frame-pointer -frounding-math    
-I/opt/lmi/local/include -fno-ms-extensions -fno-omit-frame-pointer 
-frounding-math 
/srv/cache_for_lmi/vcs/wxWidgets/src/png/arm/palette_neon_intrinsics.c
i686-w64-mingw32-gcc.exe: error: 
/srv/cache_for_lmi/vcs/wxWidgets/src/png/arm/palette_neon_intrinsics.c: No such 
file or directory
i686-w64-mingw32-gcc.exe: fatal error: no input files
compilation terminated.
make: *** [Makefile:14861: wxpng_palette_neon_intrinsics.o] Error 1
make: *** Waiting for unfinished jobs....
/srv/cache_for_lmi/vcs/wxWidgets/src/png/arm/filter_neon_intrinsics.c:20:5: 
warning: "PNG_ARM_NEON_IMPLEMENTATION" is not defined, evaluates to 0 [-Wundef]
 #if PNG_ARM_NEON_IMPLEMENTATION == 1 /* intrinsics code from pngpriv.h */
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~

The "No such file ... no input files" message seems to suggest that file
'/srv/cache_for_lmi/vcs/wxWidgets/src/png/arm/palette_neon_intrinsics.c'
doesn't exist. But then we have a warning on line twenty of that file,
suggesting that it must exist. And it does exist on my own machine:

  ls -l /srv/cache_for_lmi/vcs/wxWidgets/src/png/arm/palette_neon_intrinsics.c
  -rw-rw-r-- 1 greg greg 4608 Jul 22 13:01 
/srv/cache_for_lmi/vcs/wxWidgets/src/png/arm/palette_neon_intrinsics.c

Vadim, have you any suggestions? Is "no input files" just gcc's generic
way of telling us that something mysteriously went wrong, such as
running out of memory or disk space?