package/openjdk-bin: install to host/usr/lib/jvm

package/openjdk-bin: install to host/usr/lib/jvm

Buildroot currently installs openjdk-bin to $(HOST_DIR)/ instead of the more
traditional (for java installations) $(HOST_DIR)/usr/lib/jvm.

As described in https://bugs.busybox.net/show_bug.cgi?id=13001

"Openjdk-bin provides it's own libfreetype.so and places it into
$(HOST_DIR)/lib/. This library causes build failures with the
host-xapp_mkfontscale package due to the overwritten libfreetype.so.

mkfontscale.o: In function `doDirectory':
mkfontscale.c:(.text+0x1a80): undefined reference to `FT_Get_BDF_Property'
collect2: error: ld returned 1 exit status

Reproducing the error is done by repeating the following steps.
make host-freetype
make host-openjdk-bin
make host-xapp_mkfontscale"

There are two options for fixing this problem:

 1) add host-freetype and host-lksctp-tools as dependencies to host-openjdk-bin
    and then remove the provided libfreetype.so and libsctp.so libraries
    in a post_extract_hook.

 2) change the installation directory from $(HOST_DIR)/ to
    $(HOST_DIR)/usr/lib/jvm just like the target OpenJDK package and
    copy the entire source directories contents to the above location.

The second option provides the following advantages:
  - the directory structure is consistent with how we handle the target OpenJDK.

  - the HOST_OPENJDK_BIN_INSTALL_CMDS step is simplified.

  - packages such as Maven require directories of which we are currently not
    copying. These missing directories cause programs such as Maven to crash
    when running with an error such as
    "Can't read cryptographic policy directory: unlimited."

  - does not miss any other libraries that solution 1 would not cope with
    (e.g. libzip.so from host-libzip, or libnet.so from not-yet existing
    host-libnet, or libsctp.so from not-yet existing host-lksctp-tools)

Because the second option is both simple, easier to implement, is low-impact,
and fixes the problems described above wholly, it is the best to implement.

To implement the above changes, we must also modify the following files in the
same patch to match the host's new directory paths:

 - openjdk.mk
 - openjdk-jni-test.mk
 - openjdk-hello-world.mk

To avoid having to change all those packages in the future, expose two
new variables, HOST_OPENJDK_BIN_ROOT_DIR which contains the path where
the openjdk-bin was installed in, and JAVAC, which contains the path to
the javac compiler (modeled after the way the autoconf et al. variables
are set and exposed).

Tested with:
./support/testing/run-tests -o out -d dl tests.package.test_openjdk.TestOpenJdk

Fixes: https://bugs.busybox.net/show_bug.cgi?id=13001
Signed-off-by: Adam Duskett <Aduskett@gmail.com>
[yann.morin.1998@free.fr:
  - introduce HOST_OPENJDK_BIN_ROOT_DIR and JAVAC
  - expand and tweak the commit log
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>