SDL: workflows: Only run `cmake --install` on Unix platforms

From a4594797695b4d16137d4958455a115bcda84288 Mon Sep 17 00:00:00 2001
From: Simon McVittie <[EMAIL REDACTED]>
Date: Wed, 4 May 2022 18:13:25 +0100
Subject: [PATCH] workflows: Only run `cmake --install` on Unix platforms

The syntax used in this step assumes a Unix shell.

Signed-off-by: Simon McVittie <smcv@collabora.com>
---
 .github/workflows/main.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 353cdceb171..7a011aef594 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -86,6 +86,7 @@ jobs:
     - name: Build
       run: cmake --build build/ --config Release
     - name: Install
+      if: matrix.platform.shell == 'sh'
       run: |
         set -eu
         rm -fr DESTDIR-cmake