Makefile: stop using test -o when unlinking duplicate executables

When building executables we may end up with both `foo` and `foo.exe` in
the project's root directory. This can cause issues on Cygwin, which is
why we unlink the `foo` binary (see 6fc301b (Makefile: remove $foo
when $foo.exe is built/installed., 2007-01-10)). This step is skipped if
either:

    - `foo` is a directory, which can happen when building Git on
      Windows via MSVC (see ade2ca0 (Do not try to remove
      directories when removing old links, 2009-10-27)).

    - `foo` is a hardlink to `foo.exe`, which can happen on Cygwin (see
      0d768f7 (Makefile: building git in cygwin 1.7.0, 2008-08-15)).

These two conditions are currently chained together via `test -o`, which
is discouraged by our code style guide. Convert the recipe to instead
use an `if` statement with `&&`'d conditions, which both matches our
style guide and is easier to ready.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

Makefile

@@ -2342,7 +2342,7 @@ profile-fast: profile-clean
 
 all:: $(ALL_COMMANDS_TO_INSTALL) $(SCRIPT_LIB) $(OTHER_PROGRAMS) GIT-BUILD-OPTIONS
 ifneq (,$X)
-	$(QUIET_BUILT_IN)$(foreach p,$(patsubst %$X,%,$(filter %$X,$(ALL_COMMANDS_TO_INSTALL) $(OTHER_PROGRAMS))), test -d '$p' -o '$p' -ef '$p$X' || $(RM) '$p';)
+	$(QUIET_BUILT_IN)$(foreach p,$(patsubst %$X,%,$(filter %$X,$(ALL_COMMANDS_TO_INSTALL) $(OTHER_PROGRAMS))), if test ! -d '$p' && test ! '$p' -ef '$p$X'; then $(RM) '$p'; fi;)
 endif
 
 all::