fx macOS if [[ ]] -> [ ] bashism

Author: Anton-Latukha

scripts/install-nix-from-closure.sh

@@ -221,7 +221,7 @@ checkingRequirements() {    # This function must have checks only. Without makin
     fi
 
     # macOS support for 10.10 or higher
-    if [[ "$(uname -s)" = "Darwin" ]]; then
+    if [ "$(uname -s)" = 'Darwin' ]; then
         if [[ $(($(sw_vers -productVersion | cut -d '.' -f 2))) -lt 10 ]]; then
             error "macOS $(sw_vers -productVersion) is not supported, upgrade to 10.10 or higher"
         fi