[Yosys][Warnings] Fixed Fatal Not Git Repo Warning

Fixed a warning where "fatal: not a git repository: './/.git' was being
printed during builds of VPR.

This is caused by Yosys being included as a subtree instead of a git
submodule. The Makefile in Yosys is trying to get the current version of
git for Yosys but it cannot do it since it is not a git repo.

Just commented out the line causing the warning for now.

Author: AlexandreSinger

yosys/Makefile

@@ -149,7 +149,8 @@ YOSYS_VER := 0.32
 # back to calling git directly.
 TARBALL_GIT_REV := $(shell cat $(YOSYS_SRC)/.gitcommit)
 ifeq ($(TARBALL_GIT_REV),$$Format:%h$$)
-GIT_REV := $(shell GIT_DIR=$(YOSYS_SRC)/.git git rev-parse --short=9 HEAD || echo UNKNOWN)
+#GIT_REV := $(shell GIT_DIR=$(YOSYS_SRC)/.git git rev-parse --short=9 HEAD || echo UNKNOWN)
+GIT_REV := $(shell echo UNKNOWN)
 else
 GIT_REV := $(TARBALL_GIT_REV)
 endif