Update buildpack.toml to build and publish multi-arch buildpacks (#486)

Update .gitignore with paths for multi-arch builds

Author: jericop

.gitignore

@@ -1,3 +1,6 @@
 .bin
 build
-.idea/
+.idea/
+linux
+darwin
+windows

buildpack.toml

@@ -10,8 +10,25 @@ api = "0.7"
     uri = "https://github.com/paketo-buildpacks/pip-install/blob/main/LICENSE"
 
 [metadata]
-  include-files = ["bin/run", "bin/build", "bin/detect", "buildpack.toml"]
-  pre-package = "./scripts/build.sh"
+  include-files = [
+    "buildpack.toml",
+    "linux/amd64/bin/build",
+    "linux/amd64/bin/detect",
+    "linux/amd64/bin/run",
+    "linux/arm64/bin/build",
+    "linux/arm64/bin/detect",
+    "linux/arm64/bin/run",
+  ]
+
+  pre-package = "./scripts/build.sh --target linux/amd64 --target linux/arm64"
 
 [[stacks]]
   id = "*"
+
+[[targets]]
+  arch = "amd64"
+  os = "linux"
+
+[[targets]]
+  arch = "arm64"
+  os = "linux"