EmbeddedPkg: Only run in CI for GCC5

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=4046

This package currently does not build on non-GCC toolchains.

This change adds the package to edk2 CI so it can benefit from
ongoing CI and only tests the package against GCC.

Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Abner Chang <abner.chang@amd.com>
Cc: Daniel Schaefer <git@danielschaefer.me>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>

.azurepipelines/templates/pr-gate-build-job.yml

@@ -21,6 +21,10 @@ jobs:
   #Use matrix to speed up the build process
   strategy:
     matrix:
+      ${{ if eq(parameters.tool_chain_tag, 'GCC5') }}:
+        TARGET_GCC_ONLY:
+          Build.Pkgs: 'EmbeddedPkg'
+          Build.Targets: 'DEBUG,RELEASE,NO-TARGET,NOOPT'
       TARGET_ARM_ARMPLATFORM:
         Build.Pkgs: 'ArmPkg,ArmPlatformPkg'
         Build.Targets: 'DEBUG,RELEASE,NO-TARGET,NOOPT'