Make widl default to prefix/include instead of prefix/target/include, for windows toolchains

In these setups, we already install headers into prefix/include, in
order to save diskspace.

build-cross-tools.sh

@@ -16,6 +16,6 @@ export HOST=$CROSS_ARCH-w64-mingw32
 
 ./build-llvm.sh $PREFIX
 ./strip-llvm.sh $PREFIX
-./build-mingw-w64-widl.sh $PREFIX
+./build-mingw-w64-widl.sh $PREFIX --skip-triplet-prefix
 ./install-wrappers.sh $PREFIX
 ./prepare-cross-toolchain.sh $NATIVE $PREFIX $CROSS_ARCH

build-mingw-w64-widl.sh

@@ -2,11 +2,18 @@
 
 set -e
 
-if [ $# -lt 1 ]; then
-    echo $0 dest
+while [ $# -gt 0 ]; do
+    if [ "$1" = "--skip-triplet-prefix" ]; then
+        SKIP_TRIPLET_PREFIX=1
+    else
+        PREFIX="$1"
+    fi
+    shift
+done
+if [ -z "$PREFIX" ]; then
+    echo $0 [--skip-triplet-prefix] dest
     exit 1
 fi
-PREFIX="$1"
 # Not adding $PREFIX/bin to $PATH here, since that is expected to be
 # a cross toolchain; the compiler is expected to be in $PATH already here.
 
@@ -14,8 +21,15 @@ PREFIX="$1"
 : ${ARCHS:=${TOOLCHAIN_ARCHS-i686 x86_64 armv7 aarch64}}
 
 if [ -n "$HOST" ]; then
-    CONFIGFLAGS="--host=$HOST"
+    CONFIGFLAGS="$CONFIGFLAGS --host=$HOST"
     CROSS_NAME=$HOST-
+    EXEEXT=.exe
+fi
+if [ -n "$SKIP_TRIPLET_PREFIX" ]; then
+    CONFIGFLAGS="$CONFIGFLAGS --with-widl-includedir=$PREFIX/include"
+    # If using the same prefix, it's enough to build one single binary.
+    ALL_ARCHS="$ARCHS"
+    ARCHS=x86_64
 fi
 
 cd mingw-w64/mingw-w64-tools/widl
@@ -27,3 +41,11 @@ for arch in $ARCHS; do
     make install
     cd ..
 done
+if [ -n "$SKIP_TRIPLET_PREFIX" ]; then
+    cd $PREFIX/bin
+    for arch in $ALL_ARCHS; do
+        if [ "$arch" != "$ARCHS" ]; then
+            ln -sf $ARCHS-w64-mingw32-widl$EXEEXT $arch-w64-mingw32-widl$EXEEXT
+        fi
+    done
+fi