liblzma: Disable XL compiler optimizations in one source to avoid crash

Somehow optimizations of lzma_lzma_optimum_normal by the IBM XL C
compiler cause it to crash.  Simply disable optimizations of this source
file with a pragma.

Utilities/cmliblzma/liblzma/lzma/lzma_encoder_optimum_normal.c

@@ -8,6 +8,9 @@
 //  You can do whatever you want with this file.
 //
 ///////////////////////////////////////////////////////////////////////////////
+#if defined(__IBMC__)
+# pragma options optimize=0
+#endif
 
 #include "lzma_encoder_private.h"
 #include "fastpos.h"