clink.pl: move default linker options for MSVC=1 builds

Move the default `-ENTRY` and `-SUBSYSTEM` arguments for
MSVC=1 builds from `config.mak.uname` into `clink.pl`.
These args are constant for console-mode executables.

Add support to `clink.pl` for generating a Win32 GUI application
using the `-mwindows` argument (to match how GCC does it).  This
changes the `-ENTRY` and `-SUBSYSTEM` arguments accordingly.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>

compat/vcbuild/scripts/clink.pl

@@ -15,6 +15,7 @@
 my @lflags = ();
 my $is_linking = 0;
 my $is_debug = 0;
+my $is_gui = 0;
 while (@ARGV) {
 	my $arg = shift @ARGV;
 	if ("$arg" eq "-DDEBUG") {
@@ -124,11 +125,21 @@
 		# let's ignore those
 	} elsif ("$arg" eq "-fno-stack-protector") {
 		# eat this
+	} elsif ("$arg" eq "-mwindows") {
+		$is_gui = 1;
 	} else {
 		push(@args, $arg);
 	}
 }
 if ($is_linking) {
+	if ($is_gui) {
+		push(@args, "-ENTRY:wWinMainCRTStartup");
+		push(@args, "-SUBSYSTEM:WINDOWS");
+	} else {
+		push(@args, "-ENTRY:wmainCRTStartup");
+		push(@args, "-SUBSYSTEM:CONSOLE");
+	}
+
 	push(@args, @lflags);
 	unshift(@args, "link.exe");
 } else {

config.mak.uname

@@ -502,7 +502,7 @@ endif
 		compat/win32/trace2_win32_process_info.o \
 		compat/win32/dirent.o
 	COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DDETECT_MSYS_TTY -DENSURE_MSYSTEM_IS_SET -DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
-	BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO -ENTRY:wmainCRTStartup -SUBSYSTEM:CONSOLE
+	BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO
 	# invalidcontinue.obj allows Git's source code to close the same file
 	# handle twice, or to access the osfhandle of an already-closed stdout
 	# See https://msdn.microsoft.com/en-us/library/ms235330.aspx