Fixed an issue when npm installation failed. This happened in the case a specifc npm version (6.13.4) was preinstalled and a differnet npm version was installed. (This is triggered by a version specified in the input or by defining npm as a dependency in the
Related issue report: https://github.com/bitrise-steplib/steps-npm/issues/23.
Example error log:
$ npm "install" "-g" "npm@<version>" Error setting npm version to <version>: error running npm install: ... npm ERR! code EEXIST npm ERR! syscall symlink ...