Load namespace configuration from ld.config.txt

This change allows customization of default namespace
configuration for different executables. It also enables
target_sdk_version setup for binaries (note that this
option should explicitly be enabled in ld.config.txt).

Bug: http://b/30706810
Bug: http://b/30435785
Test: run linker-unit-tests/bionic-unit-tests, boot angler
Change-Id: Ibbe87209acf1538fc9cec04944f3d22a190c38f1
diff --git a/linker/Android.bp b/linker/Android.bp
index a43f8b3..2351e71 100644
--- a/linker/Android.bp
+++ b/linker/Android.bp
@@ -19,6 +19,7 @@
         "linker_block_allocator.cpp",
         "linker_dlwarning.cpp",
         "linker_cfi.cpp",
+        "linker_config.cpp",
         "linker_gdb_support.cpp",
         "linker_globals.cpp",
         "linker_libc_support.c",