package/openjdk-bin: new package

package/openjdk-bin: new package

Paradoxically, building OpenJDK requires a pre-existing JDK.  This
pre-existing JDK is called the "boot JDK."

The boot JDK for building JDK major version N should be a JDK of major
version N-1, so for building JDK11, JDK10 would be needed. This
requirement is an issue when building on most distributions, as the
host JDK tends to be JDK8.

The AdoptOpenJDK project provides binaries that can act as the boot
JDK to build the target JDK, which is what this package provides.

Currently, only a x86_64 host is supported, for two reasons:

1) A 32bit x86 binary distribution is not available from AdoptOpenJDK

2) We didn't had access to a host machine using an architecture other
   than x86-64

The provided unpack200 has an invalid RPATH and relies on libzlib.
When host-libzlib runs the install step, the following error is
generated:

*** ERROR: package host-libzlib installs executables without proper RPATH:
***   $(HOST_DIR)/bin/unpack200

Because unpack200 is a deprecated tool, removing it after installation
is safe and fixes the issue.

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
[Thomas:
 - fix comments in the code
 - use the more usual "cp -dpfr" command to copy files over]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>