Update binary install for best practices (eksctl-io#8359)

Replace the mv command with install for the "UNIX installation" method

Author: cloudxabide

README.md

@@ -73,7 +73,7 @@ curl -sL "https://github.com/eksctl-io/eksctl/releases/latest/download/eksctl_ch
 
 tar -xzf eksctl_$PLATFORM.tar.gz -C /tmp && rm eksctl_$PLATFORM.tar.gz
 
-sudo mv /tmp/eksctl /usr/local/bin
+sudo install -m 0755 /tmp/eksctl /usr/local/bin && rm /tmp/eksctl
 ```
 
 ### For Windows

userdocs/src/installation.md

@@ -38,7 +38,7 @@ curl -sL "https://github.com/eksctl-io/eksctl/releases/latest/download/eksctl_ch
 
 tar -xzf eksctl_$PLATFORM.tar.gz -C /tmp && rm eksctl_$PLATFORM.tar.gz
 
-sudo mv /tmp/eksctl /usr/local/bin
+sudo install -m 0755 /tmp/eksctl /usr/local/bin && rm /tmp/eksctl
 ```
 
 ### For Windows