package/openjdk: install header files to staging

These files are necessary for C or C++ programs to use the native java
interface (JNI.)

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/openjdk/openjdk.mk

@@ -20,6 +20,7 @@ endif
 
 OPENJDK_LICENSE = GPL-2.0+ with exception
 OPENJDK_LICENSE_FILES = LICENSE
+OPENJDK_INSTALL_STAGING = YES
 
 # OpenJDK requires Alsa, cups, and X11 even for a headless build.
 # host-zip is needed for the zip executable.
@@ -145,6 +146,12 @@ define OPENJDK_INSTALL_TARGET_CMDS
 	cd $(TARGET_DIR)/usr/bin && ln -snf ../..$(OPENJDK_INSTALL_BASE)/bin/* .
 endef
 
+define OPENJDK_INSTALL_STAGING_CMDS
+	mkdir -p $(STAGING_DIR)/usr/include/jvm
+	cp -dpfr $(@D)/build/linux-*-release/jdk/include/* \
+		$(STAGING_DIR)/usr/include/jvm
+endef
+
 # Demos and includes are not needed on the target
 ifeq ($(BR2_PACKAGE_OPENJDK_FULL_JDK),y)
 define OPENJDK_REMOVE_UNEEDED_JDK_DIRECTORIES