Bug 1397263 - move MIDL_FLAGS to toolkit/moz.configure; r=glandium

This is a straightforward port of MIDL_FLAGS from old-configure to
moz.configure. The only behavioral change is that it removes support for
prepending MIDL_FLAGS from the environment in configure, but I doubt anyone
uses that.

old-configure.in

@@ -263,19 +263,6 @@ case "$target" in
 
         INCREMENTAL_LINKER=1
 
-        # Set midl environment
-        case "$target" in
-        i*86-*)
-            MIDL_FLAGS="${MIDL_FLAGS} -env win32"
-            ;;
-        x86_64-*)
-            MIDL_FLAGS="${MIDL_FLAGS} -env x64"
-            ;;
-        aarch64-*)
-            MIDL_FLAGS="${MIDL_FLAGS} -env arm64"
-            ;;
-        esac
-
         unset _MSVC_VER_FILTER
 
         WRAP_STL_INCLUDES=1
@@ -318,17 +305,6 @@ case "$target" in
             AC_MSG_ERROR([windres version $WINDRES_VERSION or higher is required to build.])
         fi
 
-        if test -n "$MIDL"; then
-            case "$target" in
-            i*86-*)
-                MIDL_FLAGS="$MIDL_FLAGS --win32 -m32"
-                ;;
-            x86_64-*)
-                MIDL_FLAGS="$MIDL_FLAGS --win64 -m64"
-                ;;
-            esac
-        fi
-
         # strsafe.h on mingw uses macros for function deprecation that pollutes namespace
         # causing problems with local implementations with the same name.
         AC_DEFINE(STRSAFE_NO_DEPRECATE)
@@ -355,7 +331,6 @@ fi
 
 fi # COMPILE_ENVIRONMENT
 
-AC_SUBST(MIDL_FLAGS)
 AC_SUBST(_MSC_VER)
 
 AC_SUBST(GNU_AS)

toolkit/moz.configure

@@ -1103,8 +1103,27 @@ def check_for_midl(target, compile_environment):
 
 midl = check_prog('MIDL', midl_names, when=check_for_midl, allow_missing=True)
 
-# Needed until we move MIDL_FLAGS and --disable-accessibility from old-configure
+
+@depends(c_compiler, target, when=depends(midl, target)(lambda m, t: m and t.kernel == 'WINNT'))
+def midl_flags(c_compiler, target):
+    if c_compiler and c_compiler.type in ('msvc', 'clang-cl'):
+        env = {
+            'x86': 'win32',
+            'x86_64': 'x64',
+            'aarch64': 'arm64',
+        }[target.cpu]
+        return ['-env', env]
+
+    # mingw
+    return {
+        'x86': ['--win32', '-m32'],
+        'x86_64': ['--win64', '-m64'],
+    }[target.cpu]
+
+
+# Needed until we move --disable-accessibility from old-configure
 add_old_configure_assignment('MIDL', midl)
+set_config('MIDL_FLAGS', midl_flags)
 
 # Addon signing
 # ==============================================================