Add new user setup command banchan for module building.

It currently uses TARGET_BUILD_APPS just like tapas, but the use case is
different and it may diverge more in the future.

Test: banchan com.android.art
Test: banchan help
Test: banchan
Test: hmm
Bug: 179779520
Change-Id: Iae718e65a2a7212c741c397e03c6f9a6d5ee8951

banchanHelp.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+# locate some directories
+cd "$(dirname $0)"
+SCRIPT_DIR="${PWD}"
+cd ../..
+TOP="${PWD}"
+
+message='usage: banchan <module> ... [arm|x86|arm64|x86_64] [eng|userdebug|user]
+
+banchan selects individual APEX modules to be built by the Android build system.
+Like "tapas", "banchan" does not request the building of images for a device but
+instead configures it for an unbundled build of the given modules, suitable for
+installing on any api-compatible device.
+
+The difference from "tapas" is that "banchan" sets the appropriate products etc
+for building APEX modules rather than apps (APKs).
+
+The module names should match apex{} modules in Android.bp files, typically
+starting with "com.android.".
+
+The usage of the other arguments matches that of the rest of the platform
+build system and can be found by running `m help`'
+
+echo "$message"

envsetup.sh

@@ -9,6 +9,9 @@ Invoke ". build/envsetup.sh" from your shell to add the following functions to y
               build, and stores those selections in the environment to be read by subsequent
               invocations of 'm' etc.
 - tapas:      tapas [<App1> <App2> ...] [arm|x86|arm64|x86_64] [eng|userdebug|user]
+              Sets up the build environment for building unbundled apps (APKs).
+- banchan:    banchan <module1> [<module2> ...] [arm|x86|arm64|x86_64] [eng|userdebug|user]
+              Sets up the build environment for building unbundled modules (APEXes).
 - croot:      Changes directory to the top of the tree, or a subdirectory thereof.
 - m:          Makes from the top of the tree.
 - mm:         Builds and installs all of the modules in the current directory, and their
@@ -791,6 +794,58 @@ function tapas()
     destroy_build_var_cache
 }
 
+# Configures the build to build unbundled Android modules (APEXes).
+# Run banchan with one or more module names (from apex{} modules).
+function banchan()
+{
+    local showHelp="$(echo $* | xargs -n 1 echo | \grep -E '^(help)$' | xargs)"
+    local arch="$(echo $* | xargs -n 1 echo | \grep -E '^(arm|x86|arm64|x86_64)$' | xargs)"
+    local variant="$(echo $* | xargs -n 1 echo | \grep -E '^(user|userdebug|eng)$' | xargs)"
+    local apps="$(echo $* | xargs -n 1 echo | \grep -E -v '^(user|userdebug|eng|arm|x86|arm64|x86_64)$' | xargs)"
+
+    if [ "$showHelp" != "" ]; then
+      $(gettop)/build/make/banchanHelp.sh
+      return
+    fi
+
+    if [ $(echo $arch | wc -w) -gt 1 ]; then
+        echo "banchan: Error: Multiple build archs supplied: $arch"
+        return
+    fi
+    if [ $(echo $variant | wc -w) -gt 1 ]; then
+        echo "banchan: Error: Multiple build variants supplied: $variant"
+        return
+    fi
+    if [ -z "$apps" ]; then
+        echo "banchan: Error: No modules supplied"
+        return
+    fi
+
+    local product=module_arm
+    case $arch in
+      x86)    product=module_x86;;
+      arm64)  product=module_arm64;;
+      x86_64) product=module_x86_64;;
+    esac
+    if [ -z "$variant" ]; then
+        variant=eng
+    fi
+
+    export TARGET_PRODUCT=$product
+    export TARGET_BUILD_VARIANT=$variant
+    export TARGET_BUILD_DENSITY=alldpi
+    export TARGET_BUILD_TYPE=release
+
+    # This setup currently uses TARGET_BUILD_APPS just like tapas, but the use
+    # case is different and it may diverge in the future.
+    export TARGET_BUILD_APPS=$apps
+
+    build_build_var_cache
+    set_stuff_for_environment
+    printconfig
+    destroy_build_var_cache
+}
+
 function gettop
 {
     local TOPFILE=build/make/core/envsetup.mk