fix: update uname_os from shlib in install.sh (golangci#1944)

uname_os function in install.sh behaved incorrectly in certain
Windows environment.
This issue was fixed in client9/shlib#23

Author: WKBae

install.sh

@@ -194,9 +194,10 @@ log_crit() {
 uname_os() {
   os=$(uname -s | tr '[:upper:]' '[:lower:]')
   case "$os" in
-    cygwin_nt*) os="windows" ;;
+    msys*) os="windows" ;;
     mingw*) os="windows" ;;
-    msys_nt*) os="windows" ;;
+    cygwin*) os="windows" ;;
+    win*) os="windows" ;;
   esac
   echo "$os"
 }