[PATCH 8/8] Makefile: conditionally include GIT-VERSION-FILE

The 'clean' target is still noticeably slow on cygwin, despite the
improvements made by previous patches. For example, the second
invocation of 'make clean' below:

  $ make clean >/dev/null 2>&1
  $ make clean
  GIT_VERSION = 2.29.0.7.g273f7f9394
  ...
  $

has been timed at 6.430s on my laptop (on old core i5-4200M @ 2.50GHz,
8GB RAM, 1TB HDD).

Notice that the 'clean' target is still causing the $(GIT_VERSION) make
variable to be set (executing the GIT-VERSION-GEN script in the
process). However, the last few commits have removed all dependency on
the $(GIT_VERSION) variable from the 'clean' target. The calculation of
the git version, in order to set this variable, is thus wasted effort.

In order to eliminate such wasted effort, use the value of the internal
$(MAKECMDGOALS) variable to only '-include GIT-VERSION-FILE' when the
target is not 'clean'. (This drops the time down to 4.064s, on my laptop,
giving an improvement of 36.80%).

Signed-off-by: Ramsay Jones <redacted>
---
 Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Makefile b/Makefile
index bc9ce28bc3..ca65259e10 100644
--- a/Makefile
+++ b/Makefile

@@ -502,7 +502,9 @@ all::
 
 GIT-VERSION-FILE: FORCE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
+ifneq ($(MAKECMDGOALS),clean)
 -include GIT-VERSION-FILE
+endif
 
 # Set our default configuration.
 #

-- 
2.29.0