known-issues: clarify documentation on ignore blocks

Some regular expressions used to ignore outputs could use some extra
documentation to clarify what was being ignored.

Change-Id: Iabf3ce6964a89cdb7f9bbe8d99a3b4b8f98da59b
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>

.known-issues/make.conf

@@ -1,4 +1,6 @@
 #
-# Make blurbs
+# When filtering output of the build process, ignore lines that don't
+# provide any information that helps the invoker tell if there was an
+# error.
 #
 ^make: (Entering|Leaving) directory .*

.known-issues/testcases/block.conf

@@ -1,4 +1,7 @@
 #
+# When executing test cases, ignore the following messages as they are
+# not to be considered hard errors.
+#
 # Block line when test case cannot run in the HW due to server or connection issues
 #
 ^BLCK0/[-a-z0-9:]+	(.+)#test @[^/]+/[^:]+:[^:]+: evaluation blocked(.*)$

.known-issues/testcases/makefile.conf

@@ -1,12 +1,18 @@
 #
-# Makefile message when a test fails
+# When executing test cases under TCF, ignore the following messages
+# as they are not to be considered hard errors.
+#
+# TCF is run under make for taking advantage of the jobserver; when
+# the testcase execution fail, make will complain, which we can
+# ignore ('sommersault' was the old name of the target).
 #
 ^/tmp/tcf-[a-zA-Z0-9]+.mk:[0-9]+: recipe for target ('tcf-jobserver-run'|'sommersault') failed$
 #
-# Makefile message when a test fails, only appears on some systems
+# More of the same
 #
 ^make: \*\*\* \[(tcf-jobserver-run|sommersault)\] Error 1$
 #
-# FAIL result. There are some testcases failing
+# TCF's summary line. We don't need to consider it to determine if the
+# run failed or passed.
 #
-^FAIL0/[-a-z0-9:]*	toplevel: [0-9]+ tests \([0-9]+ passed, [0-9]+ failed, [0-9]+ blocked, [0-9]+ skipped\) - failed$
+^[A-Z]+0/[-a-z0-9:]*	toplevel: [0-9]+ tests \([0-9]+ passed, [0-9]+ failed, [0-9]+ blocked, [0-9]+ skipped\) - failed$