Bug 1257468 - Move setting MOZ_BUILD_APP subst and define to moz.configure. r=nalexander

This has the side effect of making the variable available in js/src,
which it was not in the past.

Makefile.in

@@ -17,7 +17,7 @@ default::
 
 ifndef TEST_MOZBUILD
 ifdef MOZ_BUILD_APP
-include $(topsrcdir)/$(MOZ_BUILD_APP)/build.mk
+include $(wildcard $(topsrcdir)/$(MOZ_BUILD_APP)/build.mk)
 endif
 endif
 

build/moz.configure/init.configure

@@ -580,6 +580,8 @@ def include_project_configure(project, external_source_dir, build_env, help):
 def build_project(include_project_configure, build_env, help):
     ret = os.path.dirname(os.path.relpath(include_project_configure,
                                           build_env['TOPSRCDIR']))
+    set_config('MOZ_BUILD_APP', ret)
+    set_define('MOZ_BUILD_APP', ret)
     add_old_configure_assignment('MOZ_BUILD_APP', ret)
     return ret
 

old-configure.in

@@ -3097,7 +3097,6 @@ if test -n "$MOZ_RUST"; then
     fi
 fi
 
-AC_SUBST(MOZ_BUILD_APP)
 AC_SUBST(MOZ_PHOENIX)
 AC_SUBST(MOZ_XULRUNNER)
 AC_SUBST(MOZ_B2G)
@@ -3105,8 +3104,6 @@ AC_SUBST(MOZ_MULET)
 AC_SUBST(MOZ_B2G_VERSION)
 AC_SUBST(MOZ_B2GDROID)
 
-AC_DEFINE_UNQUOTED(MOZ_BUILD_APP,$MOZ_BUILD_APP)
-
 dnl ========================================================
 dnl Ensure Android SDK and build-tools versions depending on
 dnl mobile target.