The script build.sh needs some improvements to be more readable and compliant with different shells

[aseques]

Description

The script build.sh needs some improvements to be more readable and compliant with different shells

What kind of improvement you want to add? (check one with "x", remove the others)

• Minor changes to existing features
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

Other useful information