schema: Strip absolute filename

Otherwise we potentially pollute `git diff` after `make` with local
builds.

mantle/build

@@ -30,11 +30,16 @@ schema_generate() {
     schema_version="v1"
     echo "Generating COSA Schema ${schema_version}"
 
+    out="cosa/cosa_${schema_version}.go"
     "${GOBIN}/schematyper" \
         "../src/schema/${schema_version}.json" \
-        -o "cosa/cosa_${schema_version}.go" \
+        -o "${out}.tmp" \
         --package="cosa" \
         --root-type=Build
+    # Avoid having a filename in generated code since it
+    # can vary depending on local checkout paths.
+    sed -e s,'^// generated by "\(/.*\)/schematyper\(.*\)$,// generated by "schematyper\2,' < "${out}.tmp" > "${out}"
+    rm -f "${out}.tmp"
 }
 
 host_build() {

mantle/cosa/cosa_v1.go

@@ -1,6 +1,6 @@
 package cosa
 
-// generated by "/src/cosa/mantle/bin/schematyper ../src/schema/v1.json -o cosa/cosa_v1.go --package=cosa --root-type=Build" -- DO NOT EDIT
+// generated by "schematyper ../src/schema/v1.json -o cosa/cosa_v1.go.tmp --package=cosa --root-type=Build" -- DO NOT EDIT
 
 type AliyunImage struct {
 	ImageID string `json:"id"`