ACPICA: gcc-specific: Fix possible issue with the strchr function.

Some versions of gcc implement strchr via a macro, which either
contains bugs or can provoke a bug in the compiler. This change
fixes a possible compile-time error when using this function.
The problem is usually seen when compiling the getopt.c module.
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/acpi/platform/acgcc.h

@@ -64,4 +64,15 @@
  */
 #define ACPI_UNUSED_VAR __attribute__ ((unused))
 
+/*
+ * Some versions of gcc implement strchr() with a buggy macro. So,
+ * undef it here. Prevents error messages of this form (usually from the
+ * file getopt.c):
+ *
+ * error: logical '&&' with non-zero constant will always evaluate as true
+ */
+#ifdef strchr
+#undef strchr
+#endif
+
 #endif				/* __ACGCC_H__ */