RFR: JDK-8079771 Fix SoundLibraries.gmk mismerge after JDK-8072665

[Magnus Ihse Bursie]

The merge changeset c892d81d7bba unfortunately re-introduced the X_ARCH 
define for aarch64, even though JDK-8072665 had removed it.

Bug: https://bugs.openjdk.java.net/browse/JDK-8079771
WebRev inline:
diff --git a/make/lib/SoundLibraries.gmk b/make/lib/SoundLibraries.gmk
--- a/make/lib/SoundLibraries.gmk
+++ b/make/lib/SoundLibraries.gmk
@@ -113,10 +113,6 @@
   LIBJSOUND_SRC_FILES += $(LIBJSOUND_DAUDIOFILES)
 endif # OPENJDK_TARGET_OS solaris

-
-  ifeq ($(OPENJDK_TARGET_CPU), aarch64)
-       LIBJSOUND_CFLAGS += -DX_ARCH=X_AARCH64
-  endif
 LIBJSOUND_CFLAGS += -DEXTRA_SOUND_JNI_LIBS='"$(EXTRA_SOUND_JNI_LIBS)"'

 $(eval $(call SetupNativeCompilation,BUILD_LIBJSOUND, \

/Magnus