Add -fno-strict-aliasing workaround for all GCC targets

Use a GCC option to work around aliasing bugs. See commit 013dbcd for
more details.
diff --git a/configs/bluegene-osmesa b/configs/bluegene-osmesa
index 02c69e6..d22454f 100644
--- a/configs/bluegene-osmesa
+++ b/configs/bluegene-osmesa
@@ -13,6 +13,10 @@
 CFLAGS = -O3 -ansi -pedantic -fPIC -ffast-math -D_POSIX_SOURCE -D_POSIX_C_SOURCE=199309L -D_SVID_SOURCE -D_BSD_SOURCE
 CXXFLAGS = -O3 -ansi -pedantic -fPIC -ffast-math -D_POSIX_SOURCE -D_POSIX_C_SOURCE=199309L -D_SVID_SOURCE -D_BSD_SOURC
 
+# Work around aliasing bugs - developers should comment this out
+CFLAGS += -fno-strict-aliasing
+CXXFLAGS += -fno-strict-aliasing
+
 MKLIB_OPTIONS = -static
 
 OSMESA_LIB_NAME = libOSMesa.a