(Build) Explicitly exclude PortabilityTesting headers

These headers should not be installed, but are also not mentioned
in any Makefiles. Thus the policy checker thinks they are unused.
Therefore, mentioned them in the Makefile.

RPM-369

tools/PortabilityTesting/src/Makefile.am

@@ -61,3 +61,6 @@ rose_matrix_phases_SOURCES = matrix-phases.C
 rose_matrix_phases_CPPFLAGS = $(ROSE_INCLUDES) -DDEFAULT_DATABASE='"$(DEFAULT_DATABASE)"'
 rose_matrix_phases_LDFLAGS = $(ROSE_RPATHS)
 rose_matrix_phases_LDADD = libmatrixTools.a $(ROSE_LIBS)
+
+# These headers are not installed
+not_installed_headers = matrixTools.h