Revert "Revert "Adds multi_install_skip_symbol_files field (defa..."

Revert submission 1893459-revert-1869814-vapex-multi-config-VKODFOVCWY

Reason for revert: Fix-forward in https://r.android.com/1894088
Reverted Changes:
I087bfe0dc:Revert "Adds a new prop context for choosing betwe...
I27a498506:Revert "Load persist props before starting apexd."...
Ib5344edc0:Revert "Allow users to choose between multi-instal...
If09bf590e:Revert "Adds multi_install_skip_symbol_files field...
I905dac14c:Revert "Demonstrate multi-installed APEXes."

Change-Id: I33210c8d3199338f9c898d719ed1797b629317af
diff --git a/apex/apex.go b/apex/apex.go
index 20660d3..378efe6 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -145,6 +145,16 @@
 	// Should be only used in non-system apexes (e.g. vendor: true). Default is false.
 	Use_vndk_as_stable *bool
 
+	// Whether this is multi-installed APEX should skip installing symbol files.
+	// Multi-installed APEXes share the same apex_name and are installed at the same time.
+	// Default is false.
+	//
+	// Should be set to true for all multi-installed APEXes except the singular
+	// default version within the multi-installed group.
+	// Only the default version can install symbol files in $(PRODUCT_OUT}/apex,
+	// or else conflicting build rules may be created.
+	Multi_install_skip_symbol_files *bool
+
 	// List of SDKs that are used to build this APEX. A reference to an SDK should be either
 	// `name#version` or `name` which is an alias for `name#current`. If left empty,
 	// `platform#current` is implied. This value affects all modules included in this APEX. In