Translate some linker flags

[nukyan]

I'm attempted to build libiconv with this, then it failed due to the it doesn't handles -Wl,--out-implibs,libcharset.dll.a properly.

However, I don't know whether it could now...

[wsfulton]

Can you pop some documentation into the README file and please explain how you chose each of the linker option mappings. Thanks.

[nukyan]

Can you pop some documentation into the README file and please explain how you chose each of the linker option mappings. Thanks.

--dynamicbase --disable-dynamicbase --nxcompat and --disable-nxcompat both changes DLL_CHARACTERRISTICS fields, equivalent to /DYNAMICBASE and /NXCOMPAT in MSVC.

--gc-sections enable GC of unused sections generated by -ffunction-sections and -fdata-sections in GCC. /OPT:REF elimnates packaged functions (/Gy) and datas (/Gw) in COMDAT sections in MSVC.

--out-implib changes the name of output library, /IMPLIB is the same.

--icf is equivalent to /OPT:ICF in MSVC I think.

-Bshareable is equivalent to -shared and --dll which creates a dynamic library instead of executable file.