[Fix] `nvm_get_arch`: proper value for alpine linux #1100

Job	Run time
shellcheck_matrix (bash, nvm.sh)	43s
shellcheck_matrix (sh, nvm.sh)	40s
shellcheck_matrix (dash, nvm.sh)	46s
shellcheck_matrix (ksh, nvm.sh)	52s
shellcheck_matrix (bash, install.sh)	19s
shellcheck_matrix (bash, bash_completion)	38s
shellcheck_matrix (bash, nvm-exec)	23s
shellcheck	11s
	4m 32s

Provide feedback