Clarify use of armcc in all.sh
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 5fe9fd8..6dbe544 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -282,6 +282,8 @@
 cleanup
 tests/scripts/doxygen.sh
 
+# Note - use of yotta is deprecated, and yotta also requires armcc to be on the
+# path, and uses whatever version of armcc it finds there.
 msg "build: create and build yotta module" # ~ 30s
 cleanup
 tests/scripts/yotta-build.sh