fix(build.json): spacing in error message and missing path in log

[janpio]

Motivation and Context

An error message is missing a space in the error message, and the log is missing the path completely because it doesn't concat the string

closes #648

Description

Fix both issues.

Testing

none

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[codecov-io]

Codecov Report

Merging #650 into master will not change coverage.
The diff coverage is 50%.

@@           Coverage Diff           @@
##           master     #650   +/-   ##
=======================================
  Coverage   74.24%   74.24%           
=======================================
  Files          11       11           
  Lines        1833     1833           
=======================================
  Hits         1361     1361           
  Misses        472      472

Impacted Files	Coverage Δ
bin/templates/scripts/cordova/lib/build.js	51.26% <50%> (ø)	⬆️

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[erisu]

👍 LGTM

Testing

$ cordova compile ios --device --buildConfig=buildTest.json
Reading build config file: /test/iosTestProject/buildTest.json

$ cordova compile ios --device --buildConfig=badFile.json
(node:10663) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
CordovaError: Promise rejected with non-error: 'Build config file does not exist: badFile.json'
    at /cordova/bin/cordova:29:15
    at processTicksAndRejections (internal/process/task_queues.js:85:5)

Unhandled promise rejections will need to be handled but is out-of-scope of this ticket/PR. This existed before these changes.

[brodycj]

Unhandled promise rejections will need to be handled but is out-of-scope of this ticket/PR. This existed before these changes.

Is this observation tracked in an issue?