Automatically install or produce release packages containing retdec

[PeterMatula]

Right now, if users/developers want to use retdec-idaplugin in local decompilation mode with retdec, they need to either get the pre-compiled retdec package, or build and install it themselves. Then whey need to configure retdec-idaplugin in order to use local decompilation.

This could be made much easier - retdec-idaplugin could take care of everything:

• CMake could take option that would cause it to get, build and install retdec alongside retdec-idaplugin.
• Such a build and installation could be pre-configured -> working out-of-the-box local decompilation.
• There could be a script, that automatically takes this and creates a binary release containing both retdec-idaplugin and retdec.
• Anyone using such a release package would only need to unpack it and copy it to IDA -> local decompilation would work out-of-the-box.

[s3rvac]

Just a note so we do not forget: Users will still need to install Python 3 (+ pygments) as IDA ships only with Python 2 and RetDec requires Python 3 to run.

[PeterMatula]

Fixed in 3503eb6. Release v1.0 will come shortly.