Add platform flag to usage.

Signed-off-by: Adrian Mouat <[email protected]>

README.md

@@ -18,19 +18,21 @@ $ go install github.com/chainguard-dev/incert@latest
 
 ```shell
   -ca-certs-file string
-        The path to the local CA certificates file
+    	The path to the local CA certificates file
   -ca-certs-image-url string
-        The URL of an image to extract the CA certificates from
+    	The URL of an image to extract the CA certificates from
   -dest-image-url string
-        The URL of the image to push the modified image to
+    	The URL of the image to push the modified image to
   -image-cert-path string
-        The path to the certificate file in the image (optional) (default "/etc/ssl/certs/ca-certificates.crt")
+    	The path to the certificate file in the image (optional) (default "/etc/ssl/certs/ca-certificates.crt")
   -image-url string
-        The URL of the image to append the CA certificates to
+    	The URL of the image to append the CA certificates to
   -output-certs-path string
-        Output the (appended) certificates file from the image to a local file (optional)
+    	Output the (appended) certificates file from the image to a local file (optional)
+  -platform string
+    	The platform to build for (default linux/amd64) (default "linux/amd64")
   -replace-certs
-        Replace the certificates in the certificate file instead of appending them
+    	Replace the certificates in the certificate file instead of appending them
 ```
 
 ## Example
@@ -93,4 +95,4 @@ UvupLnKWnyfjqnN9+BojZns7q2WwMgFLFT49ok8MKzWixtlnEjUwzXYuFrOZnk1P
 Ti07NEPhmg4NpGaXutIcSkwsKouLgU9xGqndXHt7CMUADTdA43x7VF8vhV929ven
 sBxXVsFy6K2ir40zSbofitzmdHxghm+Hl3s=
 -----END CERTIFICATE-----
-```
+```