--- a/configure.in
+++ b/configure.in
@@ -3489,18 +3489,22 @@ if test -n "$MOZ_NATIVE_NSS"; then
 else
    NSS_CFLAGS="-I${DIST}/include/nss"
 fi
 
 dnl ======================
 dnl Detect yasm
 dnl ======================
 
-AC_MSG_CHECKING([for YASM assembler])
-AC_CHECK_PROGS(YASM, yasm, "")
+dnl MozillaBuild ships yasm on Windows, but the configure test pops up a modal
+dnl dialog about a missing DLL.
+if test "$COMPILE_ENVIRONMENT"; then
+    AC_MSG_CHECKING([for YASM assembler])
+    AC_CHECK_PROGS(YASM, yasm, "")
+fi # COMPILE_ENVIRONMENT
 
 if test -n "$YASM"; then
   dnl Pull out yasm's version string
   YASM_VERSION=`yasm --version | $AWK '/^yasm/ { print $2 }'`
   _YASM_MAJOR_VERSION=`echo ${YASM_VERSION} | $AWK -F\. '{ print $1 }'`
   _YASM_MINOR_VERSION=`echo ${YASM_VERSION} | $AWK -F\. '{ print $2 }'`
   _YASM_RELEASE=`      echo ${YASM_VERSION} | $AWK -F\. '{ print $3 }'`
   _YASM_BUILD=`        echo ${YASM_VERSION} | $AWK -F\. '{ print $4 }'`
@@ -5726,17 +5730,16 @@ MOZ_ANGLE_RENDERER=
 MOZ_D3D_CPU_SUFFIX=
 MOZ_HAS_WINSDK_WITH_D3D=
 MOZ_D3DCOMPILER_VISTA_DLL=
 MOZ_D3DCOMPILER_VISTA_DLL_PATH=
 MOZ_DIRECTX_SDK_PATH=
 MOZ_D3DCOMPILER_XP_DLL=
 MOZ_D3DCOMPILER_XP_CAB=
 
-if test "$COMPILE_ENVIRONMENT" ; then
 case "$target_os" in
 *mingw*)
     MOZ_ANGLE_RENDERER=1
     ;;
 esac
 
 # The DirectX SDK libraries are split into x86 and x64 sub-directories
 case "${target_cpu}" in
@@ -5755,16 +5758,18 @@ MOZ_ARG_ENABLE_BOOL(require-all-d3dc-ver
 
 # This is potentially set in external mozconfig files; if it's set,
 # then the build exposes the "webgl" context name, which is reserved
 # for conformant implementations.
 if test -n "$MOZ_WEBGL_CONFORMANT"; then
   AC_DEFINE(MOZ_WEBGL_CONFORMANT)
 fi
 
+if test "$COMPILE_ENVIRONMENT"; then
+
 dnl ========================================================
 dnl D3D compiler DLL
 dnl ========================================================
 MOZ_FOUND_D3D_COMPILERS=
 
 if test -n "$MOZ_ANGLE_RENDERER"; then
   if test -z "$MOZ_D3D_CPU_SUFFIX"; then
     AC_MSG_ERROR([Couldn't determine MOZ_D3D_CPU_SUFFIX.])
@@ -6035,16 +6040,18 @@ MOZ_ARG_DISABLE_BOOL(libjpeg_turbo,
 [ --disable-libjpeg-turbo  Disable optimized jpeg decoding routines],
     MOZ_LIBJPEG_TURBO=,
     MOZ_LIBJPEG_TURBO=1)
 
 if test "$MOZ_NATIVE_JPEG" = 1 -a "$MOZ_LIBJPEG_TURBO" = 1; then
     AC_MSG_ERROR([cannot use --with-system-jpeg with --enable-libjpeg-turbo.])
 fi
 
+if test "$COMPILE_ENVIRONMENT"; then
+
 dnl Detect if we can use yasm to compile libjpeg-turbo's optimized assembly
 dnl files.
 
 if test -n "$MOZ_LIBJPEG_TURBO"; then
 
   dnl Do we support libjpeg-turbo on this platform?
   case "$OS_ARCH:$CPU_ARCH" in
   Darwin:x86)
@@ -6181,16 +6188,18 @@ if test -n "$LIBAV_FFT_ASFLAGS"; then
       AC_MSG_ERROR([Yasm 1.1 or greater is required to build with libav's optimized FFT routines, but you do not appear to have Yasm installed.  See https://developer.mozilla.org/en/YASM for more details.])
     fi
   fi
 elif test -n "$MOZ_LIBAV_FFT" -a "${CPU_ARCH}" != "arm"; then
   dnl Warn if we're not building either libav or opendl-max optimized routines.
   AC_MSG_WARN([No assembler or assembly support for libav-fft.  Using unoptimized C routines.])
 fi
 
+fi # COMPILE_ENVIRONMENT
+
 dnl ========================================================
 dnl = Enable compilation of specific extension modules
 dnl ========================================================
 
 MOZ_ARG_ENABLE_STRING(extensions,
 [  --enable-extensions     Enable extensions],
 [ for option in `echo $enableval | sed 's/,/ /g'`; do
     if test "$option" = "yes" -o "$option" = "all"; then

--- a/dom/bindings/Makefile.in
+++ b/dom/bindings/Makefile.in
@@ -20,21 +20,23 @@ css2properties_dependencies = \
   $(topsrcdir)/layout/style/nsCSSPropAliasList.h \
   $(webidl_base)/CSS2Properties.webidl.in \
   $(topsrcdir)/layout/style/PythonCSSProps.h \
   $(srcdir)/GenerateCSS2PropertiesWebIDL.py \
   $(GLOBAL_DEPS) \
   $(NULL)
 
 CSS2Properties.webidl: $(css2properties_dependencies)
-	$(CPP) $(DEFINES) $(ACDEFINES) -I$(topsrcdir)/layout/style \
-	  $(topsrcdir)/layout/style/PythonCSSProps.h | \
-	    PYTHONDONTWRITEBYTECODE=1 $(PYTHON) \
-	      $(srcdir)/GenerateCSS2PropertiesWebIDL.py \
-	      $(webidl_base)/CSS2Properties.webidl.in > $@
+	$(TOUCH) $@
+
+#	$(CPP) $(DEFINES) $(ACDEFINES) -I$(topsrcdir)/layout/style \
+#	  $(topsrcdir)/layout/style/PythonCSSProps.h | \
+#	    PYTHONDONTWRITEBYTECODE=1 $(PYTHON) \
+#	      $(srcdir)/GenerateCSS2PropertiesWebIDL.py \
+#	      $(webidl_base)/CSS2Properties.webidl.in > $@
 
 # Most of the logic for dependencies lives inside Python so it can be
 # used by multiple build backends. We simply have rules to generate
 # and include the .pp file.
 #
 # The generated .pp file contains all the important dependencies such as
 # changes to .webidl or .py files should result in code generation being
 # performed. But we do pull in file-lists.jon to catch file additions.

--- a/layout/style/Makefile.in
+++ b/layout/style/Makefile.in
@@ -14,13 +14,15 @@ csspropsidlnames_dependencies = \
   $(srcdir)/nsCSSPropAliasList.h \
   $(srcdir)/nsCSSPropsGenerated.inc.in \
   $(srcdir)/PythonCSSProps.h \
   $(srcdir)/GenerateCSSPropsGenerated.py \
   $(GLOBAL_DEPS) \
   $(NULL)
 
 nsCSSPropsGenerated.inc : $(csspropsidlnames_dependencies)
-	$(CPP) $(DEFINES) $(ACDEFINES) \
-	  $(srcdir)/PythonCSSProps.h | \
-	    PYTHONDONTWRITEBYTECODE=1 $(PYTHON) \
-	      $(srcdir)/GenerateCSSPropsGenerated.py \
-	      $(srcdir)/nsCSSPropsGenerated.inc.in > $@
+	$(TOUCH) $@
+
+#	$(CPP) $(DEFINES) $(ACDEFINES) \
+#	  $(srcdir)/PythonCSSProps.h | \
+#	    PYTHONDONTWRITEBYTECODE=1 $(PYTHON) \
+#	      $(srcdir)/GenerateCSSPropsGenerated.py \
+#	      $(srcdir)/nsCSSPropsGenerated.inc.in > $@