[build] Added 'lint' Make target

[brunoabinader]

Introduce a new Makefile target named lint - it is meant to run both clang-tidy and clang-format checks only on modified code from your local branch.

Example:

1. Rachel has a local branch named new-feature, which tracks origin/master.
2. Rachel commits all her code changes and wants to check lints and code formatting issues.
3. Rachel runs make lint and if there any changes made by either clang-tidy or clang-format, Rachel reviews and applies the changes before submitting upstream.

Caveats:

• This script assumes that your remote repository is tracked as origin.
• We currently have a .clang-format in GL native, but we might want to share it with Adds a .clang-format config everyone can agree on cpp-bootstrap#7.

Fixes #5342.

👀 @mapbox/gl

[brunoabinader]

Note: We might want to disable clang-format checks before doing a one-time run on all source code.

[brunoabinader]

Per conversation with @tmpsantos - I'll rename the current check target to coverage, and use check instead of lint for this new proposed target.

[tmpsantos]

if compdb is not a dep of lint-linux, running make lint-linux could fail no?

[brunoabinader]

We shouldn't need to call make lint-linux directly - make lint is smart enough to trigger its platform-specific variant.