Add a script to help to create flag value building rules.
The script will only extract necessary information from the value file
but it will not validate the file. The validation will defer to building
system.
For input
```
flag_value {
package: "com.android.aconfig.test"
name: "disabled_ro"
state: DISABLED
permission: READ_ONLY
}
flag_value {
package: "com.android.demoapp.test"
name: "enabled_ro"
state: DISABLED
permission: READ_WRITE
}
flag_value {
package: "com.android.aconfig.test"
name: "enabled_rw"
state: ENABLED
permission: READ_WRITE
}
```
The output Android.bp file will be like
```
VALUE_LIST_LIST = [
aconfig-local-com.android.demoapp.test,
aconfig-local-com.android.aconfig.test
]
aconfig_values {
name: "aconfig-local-com.android.demoapp.test",
package: "com.android.demoapp.test",
srcs: [
"override_values.textproto",
]
}
aconfig_values {
name: "aconfig-local-com.android.aconfig.test",
package: "com.android.aconfig.test",
srcs: [
"override_values.textproto",
]
}
```
Bug: 298692416
Test: source build/envsetup.sh && overrideflags, and then check the
output
Change-Id: Ife4063e079811e0b29046be7a6bc127cad668ed0
