[infra] Use POSIX paths for Docker containers

This makes the Housekeeper-PerCommit-InfraTests_Win task less broken.

Change-Id: Icd82b172dede83b69ed415fb03c3c47b54b5df5d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261997
Auto-Submit: Ben Wagner aka dogben <benjaminwagner@google.com>
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
diff --git a/infra/bots/gen_tasks_logic/gen_tasks_logic.go b/infra/bots/gen_tasks_logic/gen_tasks_logic.go
index 4347a66..0036552 100644
--- a/infra/bots/gen_tasks_logic/gen_tasks_logic.go
+++ b/infra/bots/gen_tasks_logic/gen_tasks_logic.go
@@ -13,6 +13,7 @@
 	"fmt"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"regexp"
 	"runtime"
@@ -944,7 +945,7 @@
 		},
 		Dependencies: []string{
 			BUILD_TASK_DRIVERS_NAME,
-			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_Release", "skia-release", filepath.Join("docker", "skia-release")),
+			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_Release", "skia-release", path.Join("docker", "skia-release")),
 		},
 		Dimensions: b.dockerGceDimensions(),
 		EnvPrefixes: map[string][]string{
@@ -984,7 +985,7 @@
 		},
 		Dependencies: []string{
 			BUILD_TASK_DRIVERS_NAME,
-			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_WASM_Release", "skia-wasm-release", filepath.Join("docker", "skia-wasm-release")),
+			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_WASM_Release", "skia-wasm-release", path.Join("docker", "skia-wasm-release")),
 		},
 		Dimensions: b.dockerGceDimensions(),
 		EnvPrefixes: map[string][]string{
@@ -1025,8 +1026,8 @@
 		},
 		Dependencies: []string{
 			BUILD_TASK_DRIVERS_NAME,
-			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_Release", "skia-release", filepath.Join("docker", "skia-release")),
-			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_WASM_Release", "skia-wasm-release", filepath.Join("docker", "skia-wasm-release")),
+			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_Release", "skia-release", path.Join("docker", "skia-release")),
+			b.createDockerImage("Housekeeper-PerCommit-CreateDockerImage_Skia_WASM_Release", "skia-wasm-release", path.Join("docker", "skia-wasm-release")),
 		},
 		Dimensions: b.dockerGceDimensions(),
 		EnvPrefixes: map[string][]string{
@@ -1607,9 +1608,9 @@
 	// Create docker image.
 	if strings.Contains(name, "CreateDockerImage") {
 		if strings.Contains(parts["extra_config"], "Skia_Release") {
-			deps = append(deps, b.createDockerImage(name, "skia-release", filepath.Join("docker", "skia-release")))
+			deps = append(deps, b.createDockerImage(name, "skia-release", path.Join("docker", "skia-release")))
 		} else if strings.Contains(parts["extra_config"], "Skia_WASM_Release") {
-			deps = append(deps, b.createDockerImage(name, "skia-wasm-release", filepath.Join("docker", "skia-wasm-release")))
+			deps = append(deps, b.createDockerImage(name, "skia-wasm-release", path.Join("docker", "skia-wasm-release")))
 		}
 	}
 
diff --git a/infra/bots/recipe_modules/docker/api.py b/infra/bots/recipe_modules/docker/api.py
index 8426676..0170d01 100644
--- a/infra/bots/recipe_modules/docker/api.py
+++ b/infra/bots/recipe_modules/docker/api.py
@@ -4,7 +4,7 @@
 # found in the LICENSE file.
 
 
-import os
+import posixpath
 from recipe_engine import recipe_api
 
 
@@ -68,7 +68,7 @@
     ]
     if docker_args:
       cmd.extend(docker_args)
-    script_rel = os.path.relpath(str(script), str(self.m.path['start_dir']))
+    script_rel = posixpath.relpath(str(script), str(self.m.path['start_dir']))
     cmd.extend([docker_image, MOUNT_SRC + '/' + script_rel])
     if args:
       cmd.extend(args)