Bug 1167474 - Remove ELFHACK_BUILD hack. r=mshal

It used to be necessary because of how elfhack was built in the past, but it
happens to be unnecessary nowadays.

build/unix/elfhack/inject/moz.build

@@ -17,8 +17,6 @@ GENERATED_SOURCES += [
     "%s.c" % cpu,
 ]
 
-DEFINES['ELFHACK_BUILD'] = True
-
 NO_PGO = True
 
 NO_VISIBILITY_FLAGS = True

build/unix/elfhack/moz.build

@@ -25,6 +25,4 @@ HOST_SOURCES += [
 
 HostProgram('elfhack')
 
-DEFINES['ELFHACK_BUILD'] = True
-
 NO_PGO = True

mozilla-config.h.in

@@ -41,11 +41,8 @@
  * Note that this should be the first #include to make sure that prtypes.h does
  * not attempt to define PRUnichar.  This includes the following hunspell-specific
  * includes.
- *
- * We don't use this to build elfhack and elf-dynstr-gc since those builds happen
- * during the export tier.  Also, disable this when building assembly files too.
  */
-#if !defined(ELFHACK_BUILD) && !defined(__ASSEMBLER__)
+#if !defined(__ASSEMBLER__)
 #include "mozilla/Char16.h"
 #endif