Bugfix: Only use git for build info if the repository is actually the right one

Also adds ability to disable check with BITCOIN_GENBUILD_NO_GIT=1 in the environment

contrib/gitian-descriptors/gitian-linux.yml

@@ -70,6 +70,7 @@ script: |
   done
 
   # Create the release tarball using (arbitrarily) the first host
+  export GIT_DIR="$PWD/.git"
   ./autogen.sh
   ./configure --prefix=${BASEPREFIX}/`echo "${HOSTS}" | awk '{print $1;}'`
   make dist

contrib/gitian-descriptors/gitian-osx.yml

@@ -80,6 +80,7 @@ script: |
   done
 
   # Create the release tarball using (arbitrarily) the first host
+  export GIT_DIR="$PWD/.git"
   ./autogen.sh
   ./configure --prefix=${BASEPREFIX}/`echo "${HOSTS}" | awk '{print $1;}'`
   make dist

contrib/gitian-descriptors/gitian-win.yml

@@ -73,6 +73,7 @@ script: |
   done
 
   # Create the release tarball using (arbitrarily) the first host
+  export GIT_DIR="$PWD/.git"
   ./autogen.sh
   ./configure --prefix=${BASEPREFIX}/`echo "${HOSTS}" | awk '{print $1;}'`
   make dist

share/genbuild.sh

@@ -16,7 +16,7 @@ fi
 DESC=""
 SUFFIX=""
 LAST_COMMIT_DATE=""
-if [ -e "$(which git 2>/dev/null)" -a "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]; then
+if [ "${BITCOIN_GENBUILD_NO_GIT}" != "1" -a -e "$(which git 2>/dev/null)" -a "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" -a "$(git status --porcelain -u no --ignored "$0" | cut -b1)" != "?" ]; then
     # clean 'dirty' status of touched files that haven't been modified
     git diff >/dev/null 2>/dev/null