Don't let ld strip relocations

This is the first step for enabling ASLR (Address Space Layout
Randomization) support. We want to enable ASLR for better protection
against exploiting security holes in Git.

The problem fixed by this commit is that `ld.exe` seems to be stripping
relocations which in turn will break ASLR support. We just make sure
it's not stripping the main executable entry.

Signed-off-by: İsmail Dönmez <ismail@i10z.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

config.mak.uname

@@ -549,9 +549,11 @@ else
 		prefix = /usr/
 		ifeq (MINGW32,$(MSYSTEM))
 			prefix = /mingw32
+			BASIC_LDFLAGS += -Wl,--pic-executable,-e,_mainCRTStartup
 		endif
 		ifeq (MINGW64,$(MSYSTEM))
 			prefix = /mingw64
+			BASIC_LDFLAGS += -Wl,--pic-executable,-e,mainCRTStartup
 		else
 			COMPAT_CFLAGS += -D_USE_32BIT_TIME_T
 			BASIC_LDFLAGS += -Wl,--large-address-aware