Issues while building PG in MS Windows, using MSYS2 and MinGW-w64

$ echo $PATH
/mingw64/bin:/usr/local/bin:/usr/bin:/bin:/c/Windows/System32:/c/Windows:/c/Windows/System32/Wbem:/c/Windows/System32/WindowsPowerShell/v1.0/:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl

$ make
make -C src all
make[1]: Entering directory '/d/Insaf/pgSource/postgresql-10.0/src'
make -C common all
make[2]: Entering directory '/d/Insaf/pgSource/postgresql-10.0/src/common'
make -C ../backend submake-errcodes
make[3]: Entering directory '/d/Insaf/pgSource/postgresql-10.0/src/backend'
make[3]: Nothing to be done for 'submake-errcodes'.
make[3]: Leaving directory '/d/Insaf/pgSource/postgresql-10.0/src/backend'
gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexce                 ss-precision=standard -O2 -DFRONTEND -I../../src/include  -I./src/include/port/win32 -DEXEC_BACKEND  "-I../../src/include/port/win32" -DBUILDING_DLL -DVAL_CONFIGURE="\"'--p                 refix=/d/Insaf/pgGcc' 'PKG_CONFIG_PATH=/mingw64/lib/pkgconfig:/mingw64/share/pkgconfig'\"" -DVAL_CC="\"gcc\"" -DVAL_CPPFLAGS="\"-DFRONTEND -I./src/include/port/win32 -DEXEC                 _BACKEND "-I../../src/include/port/win32" -DBUILDING_DLL\"" -DVAL_CFLAGS="\"-Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissin                 g-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -O2\"" -DVAL_CFLAGS_SL="\"\"" -DVAL_LDFLAGS="\"-L../../src/common -Wl,--allow-                 multiple-definition -Wl,--disable-auto-import -Wl,--as-needed\"" -DVAL_LDFLAGS_EX="\"\"" -DVAL_LDFLAGS_SL="\"\"" -DVAL_LIBS="\"-lpgcommon -lpgport -lz -lws2_32 -lm  -lws2_3                 2 \""  -c -o base64.o base64.c
In file included from ../../src/include/c.h:48:0,                from ../../src/include/postgres_fe.h:25,                from base64.c:18:
../../src/include/postgres_ext.h:47:9: error: unknown type name 'PG_INT64_TYPE'typedef PG_INT64_TYPE pg_int64;        ^~~~~~~~~~~~~
In file included from ../../src/include/postgres_fe.h:25:0,                from base64.c:18:
../../src/include/c.h:306:2: error: #error must have a working 64-bit integer datatype#error must have a working 64-bit integer datatype ^~~~~
../../src/include/c.h:446:15: error: 'FLEXIBLE_ARRAY_MEMBER' undeclared here (not in a function) char  vl_dat[FLEXIBLE_ARRAY_MEMBER]; /* Data content is here */              ^~~~~~~~~~~~~~~~~~~~~
In file included from ../../src/include/postgres_fe.h:25:0,                from base64.c:18:
../../src/include/c.h:1054:1: warning: 'PG_PRINTF_ATTRIBUTE' is an unrecognized format function type [-Wformat=]extern int snprintf(char *str, size_t count, const char *fmt,...) pg_attribute_printf(3, 4);^~~~~~
In file included from ../../src/include/c.h:1129:0,                from ../../src/include/postgres_fe.h:25,                from base64.c:18:
../../src/include/port.h:375:0: warning: "fseeko" redefined#define fseeko(a, b, c) fseek(a, b, c)

In file included from ../../src/include/c.h:101:0,                from ../../src/include/postgres_fe.h:25,                from base64.c:18:
../../src/include/pg_config_os.h:237:0: note: this is the location of the previous definition#define fseeko(stream, offset, origin) fseeko64(stream, offset, origin)

In file included from ../../src/include/c.h:1129:0,                from ../../src/include/postgres_fe.h:25,                from base64.c:18:
../../src/include/port.h:376:0: warning: "ftello" redefined#define ftello(a)  ftell(a)

In file included from ../../src/include/c.h:101:0,                from ../../src/include/postgres_fe.h:25,                from base64.c:18:
../../src/include/pg_config_os.h:240:0: note: this is the location of the previous definition#define ftello(stream) ftello64(stream)

In file included from ../../src/include/postgres_fe.h:27:0,                from base64.c:18:
../../src/include/common/fe_memutils.h:41:1: warning: 'PG_PRINTF_ATTRIBUTE' is an unrecognized format function type [-Wformat=]extern char *psprintf(const char *fmt,...) pg_attribute_printf(1, 2);^~~~~~
../../src/include/common/fe_memutils.h:42:1: warning: 'PG_PRINTF_ATTRIBUTE' is an unrecognized format function type [-Wformat=]extern size_t pvsnprintf(char *buf, size_t len, const char *fmt, va_list args) pg_attribute_printf(3, 0);^~~~~~
make[2]: *** [: base64.o] Error 1
make[2]: Leaving directory '/d/Insaf/pgSource/postgresql-10.0/src/common'
make[1]: *** [Makefile:37: all-common-recurse] Error 2
make[1]: Leaving directory '/d/Insaf/pgSource/postgresql-10.0/src'
make: *** [GNUmakefile:11: all-src-recurse] Error 2