tools: harden scripts

Refs: https://developer.apple.com/library/archive/documentation/OpenSource/Conceptual/ShellScripting/ShellScriptSecurity/ShellScriptSecurity.html#//apple_ref/doc/uid/TP40004268-CH8-SW2
Signed-off-by: Sebastian Davids <[email protected]>

Author: sdavids

tools/macos-installer/pkgbuild/npm/scripts/postinstall

@@ -1,5 +1,5 @@
 #!/bin/sh
 
 cd /usr/local/bin || exit 1
-ln -sf ../lib/node_modules/npm/bin/npm-cli.js npm
-ln -sf ../lib/node_modules/npm/bin/npx-cli.js npx
+/bin/ln -sf ../lib/node_modules/npm/bin/npm-cli.js npm
+/bin/ln -sf ../lib/node_modules/npm/bin/npx-cli.js npx