ci(win-arm64): build Harbour contribs (hbct, hbsqlit3 are required)

HbBuilder link step failed with LNK1181: cannot open input file
'hbct.lib'. Harbour contribs were disabled via HB_BUILD_CONTRIBS=no
in an earlier commit to shorten the build, but hbct.lib and
hbsqlit3.lib are both linked unconditionally by hbbuilder_win.exe.

Drop HB_BUILD_CONTRIBS=no so contribs are built and installed.
Bump cache key (v1 -> v2-contribs) to force the cache miss / rebuild
once, since the previously saved cache lacks the contrib libs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: FiveTechSoft

.github/workflows/build-windows-arm64.yml

@@ -45,7 +45,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: C:\harbour
-          key: harbour-win-arm64-v1
+          key: harbour-win-arm64-v2-contribs
           save-always: true
 
       - name: Locate GNU make on runner
@@ -77,7 +77,8 @@ jobs:
           set HB_PLATFORM=win
           set HB_INSTALL_PREFIX=C:\harbour
           set HB_BUILD_SHARED=no
-          set HB_BUILD_CONTRIBS=no
+          REM Enable contribs — hbct, hbsqlit3 are linked by HbBuilder.
+          REM Contribs add ~3-5 min but provide hbct.lib / hbsqlit3.lib.
           echo Using make: %MAKE%
           REM Serialise (-j1) so harbour.exe in src/main is fully linked
           REM before any sub-tree (src/vm, src/rtl, ...) tries to invoke it