config.mak.uname: add MSVC No_SafeExeceptionHandler option

Microsoft flipped the Windows Safe Exception Handling default
in VS2013 so that zlib became unacceptable to certain OS versions
(Vista and subsequent 32-bit OS's) without the addition of
the option -SAFESEH:NO.

Provide a switch to disable the Safe Exeption Handler when required.

The option ImageHasSafeExceptionHandlers for VS2013 is not available in
earlier versions, so use the SAFESEH:NO linker flag. See
https://msdn.microsoft.com/en-us/library/9a89h429.aspx for
further details.

This has only had limited testing due to the lack of a suitable system.

Helped-by: Yue Lin Ho <[email protected]>
Signed-off-by: Philip Oakley <[email protected]>
---
Junio/my discussion on reviews: http://marc.info/?l=git&m=143526063906215&w=2 (2015-06-25)
Patch series v1: msysgit#318
Yue Lin Ho: msysgit#318 (comment)

Author: Philip Oakley

config.mak.uname

@@ -1,5 +1,9 @@
 # Platform specific Makefile tweaks based on uname detection
 
+# Define NO_SAFESEH if you need MSVC/Visual Studio to ignore the lack of
+# Microsoft's Safe Exception Handling in libraries (such as zlib).
+# Typically required for VS2013+/32-bit compilation on Vista+ versions.
+
 uname_S := $(shell sh -c 'uname -s 2>/dev/null || echo not')
 uname_M := $(shell sh -c 'uname -m 2>/dev/null || echo not')
 uname_O := $(shell sh -c 'uname -o 2>/dev/null || echo not')
@@ -381,6 +385,11 @@ ifeq ($(uname_S),Windows)
 	PTHREAD_LIBS =
 	lib =
 	BASIC_CFLAGS += -DPROTECT_NTFS_DEFAULT=1
+
+ifdef NO_SAFESEH
+	LDFLAGS += -SAFESEH:NO
+endif
+
 ifndef DEBUG
 	BASIC_CFLAGS += -GL -Os -MD
 	BASIC_LDFLAGS += -LTCG