sqldeveloper: simplify, add darwin support

Use unpackCmd and installPhase instead of overwriting buildCommand.
This makes the derivation more readable, and adds binary stripping and
shebang patching of the output as a bonus :-)

Use makeWrapper instead of a custom wrapper script, and only export
environment variables that are used.

Set JAVA_HOME to ${jdk.home}, making it more generic and independent of
the specific jdk path being used (was a different one on zulu). This
fixes sqldeveloper on darwin, so add it to supported platforms
(plus the known-working x86_64-linux)