Allow "=" in ENV value from CLI

[nacardin]

Currently running cargo make -e RUST_LOG="my_crate=debug fails to set the RUST_LOG variable inside the makefile.

This updates the ENV parsing to allow for this.

[codecov-io]

Codecov Report

Merging #502 (4edb749) into master (3660e23) will decrease coverage by 27.90%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           master     #502       +/-   ##
===========================================
- Coverage   93.01%   65.10%   -27.91%     
===========================================
  Files          94       94               
  Lines       18352    18296       -56     
===========================================
- Hits        17070    11912     -5158     
- Misses       1282     6384     +5102     

Impacted Files	Coverage Δ
src/lib/descriptor/mod.rs	44.41% <0.00%> (-40.18%)	⬇️
src/lib/storage_test.rs	0.00% <0.00%> (-100.00%)	⬇️
src/lib/recursion_level_test.rs	0.00% <0.00%> (-100.00%)	⬇️
src/lib/cli_test.rs	2.04% <0.00%> (-94.54%)	⬇️
src/lib/scriptengine/rsscript.rs	0.00% <0.00%> (-92.31%)	⬇️
src/lib/scriptengine/rsscript_test.rs	0.00% <0.00%> (-90.09%)	⬇️
src/lib/environment/mod_test.rs	12.72% <0.00%> (-84.16%)	⬇️
src/lib/time_summary.rs	11.76% <0.00%> (-82.53%)	⬇️
src/lib/legacy_test.rs	17.64% <0.00%> (-82.36%)	⬇️
src/lib/recursion_level.rs	27.27% <0.00%> (-72.73%)	⬇️
... and 60 more

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[sagiegurari]

This looks great! thank you very much.
I'll merge once the CI is done.

[sagiegurari]

@nacardin merging. thanks a lot!!!