rt-tests: not available on avr32, too old uClibc

The old uClibc used for the AVR32 architecture does not implement
priority inheritance, therefore rt-tests cannot build.

Fixes:

  http://autobuild.buildroot.org/results/695293d889128c666174d5fe03c5deadbe4d5415/build-end.log

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/rt-tests/Config.in

@@ -1,6 +1,9 @@
 config BR2_PACKAGE_RT_TESTS
 	bool "rt-tests"
 	depends on BR2_TOOLCHAIN_HAS_THREADS
+	# Too old uClibc, does not provide priority-inheritance
+	# mutexes
+	depends on !BR2_avr32
 	help
 	  Set of utilities for testing the real-time behaviour of a
 	  Linux system.