diff --git a/tools/builder/core.sh b/tools/builder/core.sh
index caec89d6e..2dd1e90ba 100644
--- a/tools/builder/core.sh
+++ b/tools/builder/core.sh
@@ -1335,6 +1335,10 @@ build_dist() {
     dist_patch "$current_dist"
     dist_pre_build "$current_dist"
 
+    ORIG_CPPFLAGS=$CPPFLAGS
+    ORIG_CFLAGS=$CFLAGS
+    ORIG_CXXFLAGS=$CXXFLAGS
+    ORIG_OBJCXXFLAGS=$OBJCXXFLAGS
     ORIG_LDFLAGS=$LDFLAGS
     ORIG_LIBS=$LIBS
 
@@ -1344,6 +1348,10 @@ build_dist() {
         export LDFLAGS="$CXXFLAGS $LDFLAGS"
     fi
 
+    export CPPFLAGS="$LDFLAGS $(eval puts "$(dist_extra_cppflags "$current_dist")")"
+    export CFLAGS="$LDFLAGS $(eval puts "$(dist_extra_cflags "$current_dist")")"
+    export CXXFLAGS="$LDFLAGS $(eval puts "$(dist_extra_cxxflags "$current_dist")")"
+    export OBJCXXFLAGS="$LDFLAGS $(eval puts "$(dist_extra_objcxxflags "$current_dist")")"
     export LDFLAGS="$LDFLAGS $(eval puts "$(dist_extra_ldflags "$current_dist")")"
     export LIBS="$LIBS $(eval puts "$(dist_extra_libs "$current_dist")")"
 
@@ -1605,6 +1613,10 @@ build_dist() {
         fi
     fi
 
+    export CPPFLAGS="$ORIG_CPPFLAGS"
+    export CFLAGS="$ORIG_CFLAGS"
+    export CXXFLAGS="$ORIG_CXXFLAGS"
+    export OBJCXXFLAGS="$ORIG_OBJCXXFLAGS"
     export LDFLAGS="$ORIG_LDFLAGS"
     export LIBS="$ORIG_LIBS"
 
@@ -2199,6 +2211,34 @@ dist_make_install_args() {
     puts "$(table_line DIST_MAKE_INSTALL_ARGS $current_dist)" || :
 }
 
+dist_extra_cppflags() {
+    current_dist=$1
+    [ -n "$current_dist" ] || die 'dist_extra_cppflags: dist name required'
+
+    puts "$(table_line DIST_EXTRA_CPPFLAGS $current_dist)" || :
+}
+
+dist_extra_cflags() {
+    current_dist=$1
+    [ -n "$current_dist" ] || die 'dist_extra_cflags: dist name required'
+
+    puts "$(table_line DIST_EXTRA_CFLAGS $current_dist)" || :
+}
+
+dist_extra_cxxflags() {
+    current_dist=$1
+    [ -n "$current_dist" ] || die 'dist_extra_cxxflags: dist name required'
+
+    puts "$(table_line DIST_EXTRA_CXXFLAGS $current_dist)" || :
+}
+
+dist_extra_objcxxflags() {
+    current_dist=$1
+    [ -n "$current_dist" ] || die 'dist_extra_objcxxflags: dist name required'
+
+    puts "$(table_line DIST_EXTRA_OBJCXXFLAGS $current_dist)" || :
+}
+
 dist_extra_ldflags() {
     current_dist=$1
     [ -n "$current_dist" ] || die 'dist_extra_ldflags: dist name required'
diff --git a/tools/builder/mingw.sh b/tools/builder/mingw.sh
index 96aa15085..aaf80e213 100644
--- a/tools/builder/mingw.sh
+++ b/tools/builder/mingw.sh
@@ -256,6 +256,12 @@ table_insert_after DISTS cmake "dlfcn https://github.com/dlfcn-win32/dlfcn-win32
 
 table_line_replace DIST_CONFIGURE_TYPES dlfcn cmake
 
+if [ "$target_bits" -eq 32 ]; then
+    # this is necessary for a linkable libffi on i686 for whatever reason
+    # see: https://bugzilla.mozilla.org/show_bug.cgi?id=1336569
+    table_line_append DIST_EXTRA_CPPFLAGS libffi -DSYMBOL_UNDERSCORE
+fi
+
 libicu=libicu
 
 if [ -n "$(table_line DISTS libicu-target || :)" ]; then
diff --git a/tools/win/msys2-builder b/tools/win/msys2-builder
index b320e27fd..5756059b1 100755
--- a/tools/win/msys2-builder
+++ b/tools/win/msys2-builder
@@ -32,11 +32,15 @@ case "$MSYSTEM" in
         export HOST_SYSTEM=i686-w64-mingw32
         sys_base=/mingw32
         export BUILD_ROOT="$HOME/vbam-build-msys2-i686"
+        target_bits=32
+        target_cpu=i686
         ;;
     MINGW64)
         export HOST_SYSTEM=x86_64-w64-mingw32
         sys_base=/mingw64
         export BUILD_ROOT="$HOME/vbam-build-msys2-x86_64"
+        target_bits=64
+        target_cpu=x86_64
         ;;
     MSYS)
         exec "$0" "$@" -64