Fix banchan for trunk stable builds

In the trunk stable builds, we're required to have a
TARGET_RELEASE set.

For now, we hard-code this to "trunk_staging" (and leave a TODO
to accept this as a function argument).

This will have us producing valid builds in places like git_main.

Bug: 307946156
Test: None
Change-Id: Ie418aee2fad192a38beca44cd7d168e0e1b45689

envsetup.sh

@@ -947,6 +947,8 @@ function banchan()
 {
     local showHelp="$(echo $* | xargs -n 1 echo | \grep -E '^(help)$' | xargs)"
     local product="$(echo $* | xargs -n 1 echo | \grep -E '^(.*_)?(arm|x86|arm64|riscv64|x86_64|arm64only|x86_64only)$' | xargs)"
+    # TODO: Expand banchan to take release arguments (and update hmm() usage).
+    local release="trunk_staging"
     local variant="$(echo $* | xargs -n 1 echo | \grep -E '^(user|userdebug|eng)$' | xargs)"
     local apps="$(echo $* | xargs -n 1 echo | \grep -E -v '^(user|userdebug|eng|(.*_)?(arm|x86|arm64|riscv64|x86_64))$' | xargs)"
 
@@ -961,6 +963,10 @@ function banchan()
         echo "banchan: Error: Multiple build archs or products supplied: $products"
         return
     fi
+    if [ $(echo $release | wc -w) -gt 1 ]; then
+        echo "banchan: Error: Multiple build releases supplied: $release"
+        return
+    fi
     if [ $(echo $variant | wc -w) -gt 1 ]; then
         echo "banchan: Error: Multiple build variants supplied: $variant"
         return
@@ -984,6 +990,7 @@ function banchan()
     fi
 
     export TARGET_PRODUCT=$product
+    export TARGET_RELEASE=$release
     export TARGET_BUILD_VARIANT=$variant
     export TARGET_BUILD_DENSITY=alldpi
     export TARGET_BUILD_TYPE=release