Refine module name resolving in multilib build

-- Added TARGET_PREFER_32_BIT, which sets LOCAL_32_BIT_ONLY for an
   executable, if LOCAL_NO_2ND_ARCH is not true.

Name resolving in 64-bit multilib build:
-- Name resolving in PRODUCT_PACKAGES:
   foo:32 resolves to foo_32;
   foo:64 resolves to foo;
   foo resolves to both foo and foo_32 (if foo_32 is defined).

-- Name resolving for LOCAL_REQUIRED_MODULES:
   If a module is built for 2nd arch, its required module resolves to
   32-bit variant, if it exits;
   Otherwise for executable and shared library, a required module
   resolves to the default 64-bit variant; for other module classes,
   required module foo resolves to both foo and foo_32 (if foo_32 is
   defined)

Bug: 12898862
Change-Id: I5fda1a77f58814097b10b5ad2743ee25adfaecc4
diff --git a/core/executable.mk b/core/executable.mk
index 6d8734e..65319ef 100644
--- a/core/executable.mk
+++ b/core/executable.mk
@@ -3,6 +3,12 @@
 # By default, an executable is built for TARGET_ARCH.
 # To build it for TARGET_2ND_ARCH in a 64bit product, use "LOCAL_32_BIT_ONLY := true".
 
+ifeq ($(TARGET_PREFER_32_BIT),true)
+ifneq ($(LOCAL_NO_2ND_ARCH),true)
+LOCAL_32_BIT_ONLY := true
+endif
+endif
+
 ifeq ($(TARGET_IS_64_BIT)|$(LOCAL_32_BIT_ONLY),true|true)
 LOCAL_2ND_ARCH_VAR_PREFIX := $(TARGET_2ND_ARCH_VAR_PREFIX)
 else