build: Allow 'make quickcheck' test-tool args to be overridden.

A typical use for this is for packagers who want to increase
the default timeout:

  make quickcheck QUICKCHECK_TEST_TOOL_ARGS="-t 300"
(cherry picked from commit 806b6e01506dea4eae68ac3e468d9398d63cafcb)

diff --git a/Makefile.am b/Makefile.am
index e1ddf0d..ca31727 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -219,7 +219,7 @@ CLEANFILES = \
 # is NOT a substitute for proper testing!
 
 quickcheck:
-       ./run test-tool/libguestfs-test-tool
+       ./run test-tool/libguestfs-test-tool $(QUICKCHECK_TEST_TOOL_ARGS)
 
 # Make binary distribution.