community/llvm-libunwind: add support for cross compilation

community/llvm-libunwind/APKBUILD

@@ -22,6 +22,12 @@ build() {
 	mkdir -p "$builddir/build"
 	cd "$builddir/build"
 
+	local crossopts=''
+	[ "$CBUILD" != "$CHOST" ] && crossopts="
+		-DCMAKE_SYSTEM_NAME=Linux
+		-DCMAKE_HOST_SYSTEM_NAME=Linux
+		-DLIBUNWIND_SYSROOT=$CBUILDROOT"
+
 	cmake .. \
 		-DCMAKE_BUILD_TYPE=MinSizeRel \
 		-DCMAKE_C_FLAGS_MINSIZEREL_INIT="$CFLAGS" \
@@ -30,8 +36,8 @@ build() {
 		-DCMAKE_INSTALL_PREFIX=/usr \
 		\
 		-DLLVM_CONFIG_PATH="/usr/lib/llvm$_llvmver/bin/llvm-config" \
-		-DLIBUNWIND_HAS_NODEFAULTLIBS_FLAG=OFF
-
+		-DLIBUNWIND_HAS_NODEFAULTLIBS_FLAG=OFF \
+		$crossopts
 	make
 }