Make some CI test code optional

The only present test case rebuilt, installed and booted the kernel.
Now let's make the install and boot steps optional, just on explicit
request. Skipping these steps will be the default behaviour, at least
for now.

You can override the default by setting variable "JUST_BUILD" in the
environment the test runs in. The variable defaults to "yes" which
means the test will just build the kernel. If you use JUST_BUILD=no
(or JUST_BUILD=false or JUST_BUILD=0) then the test will not only
build but install and boot the kernel, too.

Note that the acceptable values of JUST_BUILD are case insensitive.

tests/Sanity/rebuild-kernel-and-reboot/runtest.sh

@@ -28,6 +28,15 @@
 
 export AVC_ERROR='+no_avc_check'
 
+case "$JUST_BUILD" in
+    0|[Ff][Aa][Ll][Ss][Ee]|[Nn][Oo])
+        JUST_BUILD=no
+        ;;
+    *)
+        JUST_BUILD=yes
+        ;;
+esac
+
 LD="${LD:-$(which ld)}"
 GCC="${GCC:-$(which gcc)}"
 
@@ -54,6 +63,7 @@ rlJournalStart
         rlLogInfo "PACKAGES=$PACKAGES"
         rlLogInfo "KERNEL=$KERNEL"
         rlLogInfo "REQUIRES=$REQUIRES"
+        rlLogInfo "JUST_BUILD=$JUST_BUILD"
         rlLogInfo "COLLECTIONS=$COLLECTIONS"
         rlLogInfo "SKIP_COLLECTION_METAPACKAGE_CHECK=$SKIP_COLLECTION_METAPACKAGE_CHECK"
 
@@ -130,8 +140,8 @@ rlJournalStart
             rlBundleLogs "Build-log" BUILD_LOG
         rlPhaseEnd
 
-        # Only install new kernel and reboot if the kernel build went successful
-        if [ "$RPMBUILD_OK" = "yes" ]; then
+        # Install and boot the new kernel only if it's requested *and* the build was successful
+        if [ "$JUST_BUILD" = 'no' ] && [ "$RPMBUILD_OK" = "yes" ]; then
             rlPhaseStartTest "Install"
                 RPMS="$(ls -1 $TmpDir/RPMS/*/*.rpm | grep -v kernel-selftests-internal | tr '\n' ' ')"
 
@@ -162,10 +172,16 @@ rlJournalStart
         fi
     fi
 
+    # Verify the build ID only if its install and boot were requested
+    if [ "$JUST_BUILD" = 'no' ]; then
         rlPhaseStartTest "Test"
+            if ! [ "$AFTER_REBOOT" = 'yes' ]; then
+                rlFail 'Not rebooted. Probably rhts-reboot did not work.'
+            fi
             rlLogInfo "$(uname -a)"
             rlRun "uname -r | grep $RPM_BUILD_ID"
         rlPhaseEnd
+    fi
 
     rlPhaseStartCleanup
     rlPhaseEnd