Remove 'build' from .gitignore

[sberyozkin]

Fixes #192

[rdebusscher]

Any reason why the contents of build directories needs to be in the git repo? It was probably there for a reason

[sberyozkin]

@rdebusscher Hi, see #192

It is not a big deal that for example a future builder API would have builder package as opposed to build (the latter is more compact) but keeping build ignored just in case is not worth on its own, neither Eclipse nor IntelliJ nor Maven apparently have this folder generated.
I've no strong opinion but I'd like to see someone actually saying, wait. my IDE generates build.
It was added here:
792c581#diff-a084b794bc0759e7a6b77810e01874f2

Let me ask @starksm64 Hi Scott, was there any particular reason build was added in .gitignore ?

My best bet is that it is the Ant legacy and build is a copy and paste side-effect, but I won't rush

[sberyozkin]

For the record, smallrye-jwt JWT builder API which the build JWT PR was based around has a build sub-package but we haven't seen anyone reporting any issues around it in the Quarkus/smallrye-jwt land for the last 6+ months.

[rdebusscher]

Then there was maybe a typo in the .gitignore initially when ant build directory was meant to exclude (should be /build instead of build/)