errors when building gcc-9.1.0 under cygwin

I received this error:

>/usr/local/contrib/gcc-9.1.0/libbacktrace/pecoff.c: In function ‘coff_add’:
/usr/local/contrib/gcc-9.1.0/libbacktrace/pecoff.c:656:37: error: pointer of type ‘void *’ used in arithmetic [-Werror=pointer-arith]
  656 |       memcpy (&fhdr, fhdr_view.data + 4, sizeof fhdr);
      |                                     ^
/usr/local/contrib/gcc-9.1.0/libbacktrace/pecoff.c:690:22: error: pointer of type ‘void *’ used in arithmetic [-Werror=pointer-arith]
  690 |     (sects_view.data + fhdr.size_of_optional_header);
      |                      ^
/usr/local/contrib/gcc-9.1.0/libbacktrace/pecoff.c:730:45: error: pointer of type ‘void *’ used in arithmetic [-Werror=pointer-arith]
  730 |       str_size = coff_read4 (syms_view.data + syms_size);
      |                                             ^
cc1: all warnings being treated as errors
make[3]: *** [Makefile:1190: pecoff.lo] Error 1
make[3]: Leaving directory '/usr/local/contrib/gcc_build/x86_64-pc-cygwin/libbacktrace'
make[2]: *** [Makefile:973: all] Error 2
make[2]: Leaving directory '/usr/local/contrib/gcc_build/x86_64-pc-cygwin/libbacktrace'
make[1]: *** [Makefile:19155: all-target-libbacktrace] Error 2
make[1]: Leaving directory '/usr/local/contrib/gcc_build'
make: *** [Makefile:996: all] Error 2

when make was executing the following:

libtool: compile:  /usr/local/contrib/gcc_build/./gcc/xgcc -B/usr/local/contrib/gcc_build/./gcc/ -B/usr/local/x86_64-pc-cygwin/bin/ -B/usr/local/x86_64-pc-cygwin/lib/ -isystem /usr/local/x86_64-pc-cygwin/include -isystem /usr/local/x86_64-pc-cygwin/sys-include -DHAVE_CONFIG_H -I. -I/usr/local/contrib/gcc-9.1.0/libbacktrace -I /usr/local/contrib/gcc-9.1.0/libbacktrace/../include -I /usr/local/contrib/gcc-9.1.0/libbacktrace/../libgcc -I ../libgcc -funwind-tables -frandom-seed=pecoff.lo -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmissing-format-attribute -Wcast-qual -Werror -g -O2 -pedantic -fomit-frame-pointer -m64 -mtune=sandybridge -march=sandybridge -c /usr/local/contrib/gcc-9.1.0/libbacktrace/pecoff.c -o pecoff.o

my make version is GNU Make 4.2.1 for x86_64-unknown-cygwin and my current GCC is 7.4.0

I typed the configure program inside the source as the following,

bash
/usr/local/contrib/gcc-9.1.0/configure --enable-static --disable-shared --with-mpfr-include=/usr/local/include/ --with-mpfr-lib=/usr/local/lib/ --with-mpc-include=/usr/local/include/ --with-mpc-lib=/usr/local/lib/ --with-gmp-include=/usr/local/include/ --with-gmp-lib=/usr/local/lib/ CC=gcc CFLAGS="-O2 -pedantic -fomit-frame-pointer -m64 -mtune=sandybridge -march=sandybridge"

for matter of compatibility with the other configurations I made for the dependencies mpfr, mpc and gmp all of which shared the same compiling options. --enable-static and --disable-shared is for the configuration to not look for shared libraries, choosing static ones instead, otherwise I run into errors building the dependencies, because gmp is built on static libraries

project on fossies website: gcc-9.1.0 source and the configure file: configuration step

After testing somethings I came to realize I need some more deffinitive ways to disable the pointer-arith error of the compiler. I am having issues with it because there are lots of rewrites of macros and variables on the Makefile and many candidates for change, which by the way I yet dont understand precisely the logic of their deffinitions. I tested changes at the lines it says it is giving errors, at the Makefile and on some variables like:

RECURSE_FLAGS_TO_PASS TFLAGS TARGET_FLAGS_TO_PASS RECURSE_FLAGS_TO_PASS

and on terminal with BUILD_CONFIG and EXTRA_BUILD_FLAGS

trying to disable the warning, also I sometimes passed with CXX_FLAGS or CFLAGS, usually with CFLAGS, since the install documentation makes many refferences to it

I could get the make command to print:

[ -f stage_final ] || echo stage3 > stage_final
RECURSE_FLAGS_TO_PASS+=CFLAGS+=-W
TFLAGS+=CFLAGS+=-W
TARGET_FLAGS_TO_PASS+=CFLAGS+=-W
RECURSE_FLAGS_TO_PASS+=CFLAGS=-W

which I think may be some progress