SL-19242: Pass channel and imagename to sign-pkg-mac/action.yaml.

The viewer_manifest.py logic to determine the name of the viewer installer
.dmg is a little convoluted. Make it tell viewer-build-util/sign-pkg-mac that
name, rather than passing it all the relevant inputs and composing it
redundantly.

sign-pkg-mac also wants the viewer channel to determine the application name.

.github/workflows/build.yaml

@@ -24,6 +24,7 @@ jobs:
     outputs:
       viewer_channel: ${{ steps.build.outputs.viewer_channel }}
       viewer_version: ${{ steps.build.outputs.viewer_version }}
+      imagename: ${{ steps.build.outputs.imagename }}
     env:
       AUTOBUILD_ADDRSIZE: 64
       AUTOBUILD_BUILD_ID: ${{ github.run_id }}
@@ -280,6 +281,9 @@ jobs:
     steps:
       - name: Sign and package Mac viewer
         uses: secondlife/viewer-build-util/sign-pkg-mac@main
+        with:
+          channel: ${{ needs.build.outputs.viewer_channel }}
+          imagename: ${{ needs.build.outputs.imagename }}
 
   post-windows-symbols:
     needs: build

indra/newview/viewer_manifest.py

@@ -1273,6 +1273,7 @@ def package_finish(self):
         volname=CHANNEL_VENDOR_BASE+" Installer"  # DO NOT CHANGE without understanding comment above
 
         imagename = self.installer_base_name()
+        self.set_github_output('imagename', imagename)
 
         sparsename = imagename + ".sparseimage"
         finalname = imagename + ".dmg"
@@ -1292,7 +1293,7 @@ def package_finish(self):
             
         try:
             devfile = re.search("/dev/disk([0-9]+)[^s]", hdi_output).group(0).strip()
-            volpath = re.search('HFS\s+(.+)', hdi_output).group(1).strip()
+            volpath = re.search(r'HFS\s+(.+)', hdi_output).group(1).strip()
 
             # Copy everything in to the mounted .dmg