I tried, and while everything compiles just fine, using the newly built FB fails to compile any example program
I get the following errors
renaming the directory lib\freebasic\cygwin-x86_64 to lib\freebasic\win64 eliminates the directory not found and after copying the cygwin version of the missing libraries and crt2.o to lib\freebasic\win64, I geterror 23: File not found, crt2.o
ld: cannot find G:\cygwin64\usr\local\bin\..\lib\freebasic\win64\fbextra.x: No such file or directory
ld: cannot find G:\cygwin64\usr\local\bin\..\lib\freebasic\win64\fbrt0.o: No such file or directory
ld: cannot find -lfb
ld: cannot find -lfbgfx
ld: cannot find -lmsvcrt
ld: cannot find -lmingw32
ld: cannot find -lmingwex
ld: cannot find -lmoldname
/usr/lib/gcc/x86_64-pc-cygwin/7.3.0/crtbegin.o:cygming-crtbegin.c:(.text+0x16): undefined reference to `__cxa_atexit'
/usr/lib/gcc/x86_64-pc-cygwin/7.3.0/crtbegin.o:cygming-crtbegin.c:(.text+0x16): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `__cxa_atexit'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(init.o):init.c:(.text+0x9c): undefined reference to `__getreent'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(init.o):init.c:(.text+0x9c): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `__getreent'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x1af): undefined reference to `__locale_ctype_ptr'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x1af): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `__locale_ctype_ptr'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x1c7): undefined reference to `__locale_ctype_ptr'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x1c7): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `__locale_ctype_ptr'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x221): undefined reference to `__locale_ctype_ptr'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x221): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `__locale_ctype_ptr'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x2e1): undefined reference to `__locale_ctype_ptr'
G:\cygwin64\usr\local\bin\..\lib\freebasic\win64/libfb.a(io_input.o):io_input.c:(.text+0x2e1): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `__locale_ctype_ptr'