scripted-diff: Rename share/genbuild.sh macros to more meaningful ones

-BEGIN VERIFY SCRIPT-
sed -i 's/\bDESC\b/GIT_TAG/' share/genbuild.sh
sed -i 's/\bSUFFIX\b/GIT_COMMIT/g' share/genbuild.sh
-END VERIFY SCRIPT-

share/genbuild.sh

@@ -18,8 +18,8 @@ else
     exit 1
 fi
 
-DESC=""
-SUFFIX=""
+GIT_TAG=""
+GIT_COMMIT=""
 if [ "${BITCOIN_GENBUILD_NO_GIT}" != "1" ] && [ -e "$(command -v git)" ] && [ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]; then
     # clean 'dirty' status of touched files that haven't been modified
     git diff >/dev/null 2>/dev/null
@@ -27,18 +27,18 @@ if [ "${BITCOIN_GENBUILD_NO_GIT}" != "1" ] && [ -e "$(command -v git)" ] && [ "$
     # if latest commit is tagged and not dirty, then override using the tag name
     RAWDESC=$(git describe --abbrev=0 2>/dev/null)
     if [ "$(git rev-parse HEAD)" = "$(git rev-list -1 $RAWDESC 2>/dev/null)" ]; then
-        git diff-index --quiet HEAD -- && DESC=$RAWDESC
+        git diff-index --quiet HEAD -- && GIT_TAG=$RAWDESC
     fi
 
     # otherwise generate suffix from git, i.e. string like "59887e8-dirty"
-    SUFFIX=$(git rev-parse --short HEAD)
-    git diff-index --quiet HEAD -- || SUFFIX="$SUFFIX-dirty"
+    GIT_COMMIT=$(git rev-parse --short HEAD)
+    git diff-index --quiet HEAD -- || GIT_COMMIT="$GIT_COMMIT-dirty"
 fi
 
-if [ -n "$DESC" ]; then
-    NEWINFO="#define BUILD_DESC \"$DESC\""
-elif [ -n "$SUFFIX" ]; then
-    NEWINFO="#define BUILD_SUFFIX $SUFFIX"
+if [ -n "$GIT_TAG" ]; then
+    NEWINFO="#define BUILD_DESC \"$GIT_TAG\""
+elif [ -n "$GIT_COMMIT" ]; then
+    NEWINFO="#define BUILD_SUFFIX $GIT_COMMIT"
 else
     NEWINFO="// No build information available"
 fi