make release tag discovery more robust (#2170)

### Ticket
closes #2169

### Problem description
Current git stansa `git describe --tags --abbrev=0` can pick up tags
from personal dev branches, which will results in empty
TTMLIR_VERSION_MAJOR/TTMLIR_VERSION_MINOR defs and a broken build.

### What's changed
Final change is to add a glob filter that will select the latest tag
matching `v<digit>*.<digit>*`, which is compatible with our current
release tag format but should also reduce the probability that a
personal dev tag gets picked up.

Note that using `git tag --merged main ...` was promising in local
builds but seems problematic in CI which uses detached head clones.

### Checklist
Tested against multiple tags in a dev branch and observed a CI run
succeed with the latest changes.

.github/actions/build-tt-mlir-action/action.yaml

@@ -151,7 +151,7 @@ runs:
     - name: Get Latest Tag and Version
       shell: bash
       run: |
-        latest_tag=$(git describe --tags --abbrev=0)
+        latest_tag=$(git describe --tags --match 'v[0-9]*.[0-9]*' --abbrev=0)
         latest_tag=${latest_tag#v}
         echo "latest_tag=$latest_tag" >> $GITHUB_ENV
         commit_count=$(git rev-list ${{ env.latest_tag }}..HEAD --count)

cmake/modules/TTMLIRVersion.cmake

@@ -6,9 +6,10 @@ execute_process(
   OUTPUT_STRIP_TRAILING_WHITESPACE
 )
 
-# get the latest tag from Git
+# get the latest tag from git matching 'v<major>.<minor>' format
+# (note: matching a glob(7) pattern, not a regex)
 execute_process(
-  COMMAND git describe --tags --abbrev=0
+  COMMAND git describe --tags --match v[0-9]*.[0-9]* --abbrev=0
   WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}
   OUTPUT_VARIABLE GIT_TAG
   OUTPUT_STRIP_TRAILING_WHITESPACE