[PATCH] Makefile: fix OPENSBI_VERSION_GIT build with submodules

[Daniel Henrique Barboza]

When building OpenSBI via a submodule, OPENSBI_VERSION_GIT can be left
unset in case '.git' isn't a dir. This is the case when building OpenSBI
as a QEMU submodule:

$ cat .git
gitdir: ../../.git/modules/roms/opensbi

As a result, building OpenSBI tag v1.5.1 in QEMU will result in a binary
that will have "OpenSBI v1.5" as a banner.

Use "git rev-parse --git-dir" instead of checking if '.git' is a dir to
detect if the current dir is a git repo.

Signed-off-by: Daniel Henrique Barboza <dbarboza at ventanamicro.com>
---
 Makefile | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 9c7fd4d..1497174 100644
--- a/Makefile
+++ b/Makefile
@@ -91,7 +91,13 @@ endif
 # Find library version
 OPENSBI_VERSION_MAJOR=`grep "define OPENSBI_VERSION_MAJOR" $(include_dir)/sbi/sbi_version.h | sed 's/.*MAJOR.*\([0-9][0-9]*\)/\1/'`
 OPENSBI_VERSION_MINOR=`grep "define OPENSBI_VERSION_MINOR" $(include_dir)/sbi/sbi_version.h | sed 's/.*MINOR.*\([0-9][0-9]*\)/\1/'`
-OPENSBI_VERSION_GIT=$(shell if [ -d $(src_dir)/.git ]; then git describe 2> /dev/null; fi)
+OPENSBI_VERSION_GIT=
+
+# Detect 'git' presence before issuing 'git' commands
+GIT_AVAIL=$(shell command -v git 2> /dev/null)
+ifneq ($(GIT_AVAIL),)
+OPENSBI_VERSION_GIT=$(shell git rev-parse --git-dir &> /dev/null && git describe 2> /dev/null)
+endif
 
 # Setup compilation commands
 ifneq ($(LLVM),)
-- 
2.45.2