coin: Add CI_PATH_SEP env var with value of host OS path separator

Can be useful in the future for path construction, to avoid adding
two different instructions where the only difference is the path
style.

Pick-to: 6.2 6.3
Change-Id: Id67b287a2d9f67889dcc5c4fc7781d9ef60a56be
Reviewed-by: Toni Saario <toni.saario@qt.io>

coin/instructions/prepare_building_env.yaml

@@ -8,6 +8,24 @@ instructions:
     variableName: CMAKE_GENERATOR
     variableValue: Ninja
 
+  # Set path separator based on host platform.
+  # \ on Windows (double \\ for escaping the backslash)
+  # / on UNIX
+  - type: EnvironmentVariable
+    variableName: CI_PATH_SEP
+    variableValue: "\\"
+    enable_if:
+      condition: property
+      property: host.os
+      equals_value: Windows
+  - type: EnvironmentVariable
+    variableName: CI_PATH_SEP
+    variableValue: "/"
+    disable_if:
+      condition: property
+      property: host.os
+      equals_value: Windows
+
 
   # Export ICC specific env. variables
   - type: Group