XL: Drop -qalias=noansi from default C flags

This was added without explanation by commit v2.8.2~1138 (Add initial XL
C compiler flags for safer builds, 2009-09-30).  It is not consistent
with our default C++ flags for XL and disables several optimizations, so
drop it from our default flags for C.

Suggested-by: Todd Gamblin <[email protected]>

Modules/Compiler/XL-ASM.cmake

@@ -1,9 +1,8 @@
 set(CMAKE_ASM_VERBOSE_FLAG "-V")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
-# -qalias=noansi = Turns off type-based aliasing completely (safer optimizer)
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_ASM_FLAGS_INIT "-qthreaded -qalias=noansi -qhalt=e -qsourcetype=assembler")
+set(CMAKE_ASM_FLAGS_INIT "-qthreaded -qhalt=e -qsourcetype=assembler")
 
 set(CMAKE_ASM_FLAGS_DEBUG_INIT "-g")
 set(CMAKE_ASM_FLAGS_RELEASE_INIT "-O -DNDEBUG")

Modules/Compiler/XL-C.cmake

@@ -4,6 +4,5 @@ set(CMAKE_C_FLAGS_RELEASE_INIT "${CMAKE_C_FLAGS_RELEASE_INIT} -DNDEBUG")
 set(CMAKE_C_FLAGS_MINSIZEREL_INIT "${CMAKE_C_FLAGS_MINSIZEREL_INIT} -DNDEBUG")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe
-# -qalias=noansi = Turns off type-based aliasing completely (safer optimizer)
 # -qhalt=e       = Halt on error messages (rather than just severe errors)
-set(CMAKE_C_FLAGS_INIT "-qthreaded -qalias=noansi -qhalt=e")
+set(CMAKE_C_FLAGS_INIT "-qthreaded -qhalt=e")