[installer] check TORNADO_SDK upfront

[jjfumero]

Description

It checks for the TORNADO_SDK env variable upfront instead of compiling the whole TornadoVM and getting the error at the end, forcing to recompile the whole project.

Problem description

If the TORNADO_SDK was not defined, TornadoVM only emits the error when maven finishes the Java build.

Backend/s tested

Mark the backends affected by this PR.

• [X] OpenCL
• [X] PTX
• [X] SPIRV

OS tested

Mark the OS where this PR is tested.

• [X] Linux
• [ ] OSx
• [ ] Windows

Did you check on FPGAs?

If it is applicable, check your changes on FPGAs.

• [ ] Yes
• [X] No

How to test the new patch?

$ make
$ bin/compile --jdk jdk21 --backend opencl
Checking TORNADO_SDK env variable ................ [ERROR] 
	 TORNADO_SDK env variable not defined

 	 Suggestion (Linux and OSx): run `source setvars.sh`
 
 	 Suggestion (Windows): run `setvars.cmd`

$ source setvars.sh
$ make 

ource setvars.sh 
 juan   feat/install/checker … 3  ~  tornadovm  TornadoVM  make
bin/compile --jdk jdk21 --backend opencl
Checking TORNADO_SDK env variable ................ [OK]
mvn -Popencl-backend,ptx-backend,spirv-backend clean
...