Fix #623, show stderr output on doc build workflow

Tee the stderr output to the console, so if the "Build Documentation"
step fails in this workflow, the errors will be visible in the log.

Without this, the errors are hidden in a file that is never shown nor
uploaded so it cannot be seen what went wrong.

.github/workflows/build-deploy-doc.yml

@@ -97,7 +97,7 @@ jobs:
 
       - name: Add Repo To Build
         if: ${{ inputs.app-name != '' }}
-        run: sed -i '/list(APPEND MISSION_GLOBAL_APPLIST/a list(APPEND MISSION_GLOBAL_APPLIST ${{ inputs.app-name }})' sample_defs/targets.cmake 
+        run: echo 'set(MISSION_GLOBAL_APPLIST ${{ inputs.app-name }})' >> sample_defs/targets.cmake
 
       - name: Make Prep
         run: make prep
@@ -112,7 +112,7 @@ jobs:
 
       - name: Build Document
         run: |
-          make -C build ${{ matrix.target }} > ${{ matrix.target }}_stdout.txt 2> ${{ matrix.target }}_stderr.txt
+          make -C build ${{ matrix.target }} 2>&1 > ${{ matrix.target }}_stdout.txt | tee ${{ matrix.target }}_stderr.txt
           mv build/docs/${{ matrix.target }}/${{ matrix.target }}-warnings.log .
 
       - name: Archive Document Build Logs