Add --build optional parameter to mkdocker.sh to allow use of podman

[kgibm]

Fixes #15887

Adds an optional parameter to --build to specify the container engine (default docker). If --build without an engine is specified and docker is not on $PATH and podman is on $PATH, then the engine will default to podman. If the engine is not on $PATH, an error is printed.

$ bash mkdocker.sh --tag=openj9 --dist=ubuntu --version=16.04 --gitcache=no --jdk=8 --build=podman
[...]
COMMIT openj9
--> fc6baf7ddcb
Successfully tagged localhost/openj9:latest

Signed-off-by: Kevin Grigorenko kevin.grigorenko@us.ibm.com

[keithc-ca]

What do you think about using the existing --build option instead?

Given a value it would specify the builder to use (still defaulting to docker).

Either way, I think some validation of the value is appropriate (at least that it names an executable).

[kgibm]

What do you think about using the existing --build option instead?

Given a value it would specify the builder to use (still defaulting to docker).

Either way, I think some validation of the value is appropriate (at least that it names an executable).

That's a good idea. I'll also add validation. I'm out of the office the rest of this week but will pick this up on Monday.

[kgibm]

@keithc-ca Please re-review

[dsouzai]

@kgibm could you also update the PR subject / description to reflect the current changes?

[kgibm]

@kgibm could you also update the PR subject / description to reflect the current changes?

Sure. Updated.

[keithc-ca]

Please squash in preparation for merging.

[kgibm]

Squashed and pushed