Update git submodules

* Update external/lk from branch 'master'
  to 5247c42ccc94917d1423104abbc7ae8330ebab40
  - Add Rust host flags for proc macros
    
    Adds a separate GLOBAL_HOST_RUSTFLAGS to configure Rust for building
    host crates.
    
    Test: build.py
    Bug: 229156386
    Change-Id: Id927c785e908975f2b9445b3868bdaabb89231bc
    

* Update trusty/kernel from branch 'master'
  to e7c4b8c3f08695467f175b848ce4891c0bd3f0d6
  - Add Rust flags for host crate builds
    
    Adds an output directory and support for building Rust host crates for
    the host architecture to use for proc macros.
    
    Test: build.py
    Bug: 229156386
    Change-Id: Icabee99150a05cb9f5dd5c67451b589d32c28cf1
    

* Update trusty/user/base from branch 'master'
  to 87be0526167ab63316b9b27962a0b81b336c65aa
  - [rust] Add proc-macro2, quote, and syn crates
    
    Adds host crate build files for external proc macro support crates.
    
    Test: build.py
    Bug: 229156386
    Change-Id: Ie71135110a6641b0a79573f16d8a4b048dabef8d
    
  - [rust] Add build system support for proc macro crates
    
    Adds build system support for building proc macro crates and their
    dependencies for the host system.
    
    Test: build.py
    Bug: 229156386
    Change-Id: I648064a509a0198b784605e0cc846c0808aa9e37
    

* Update trusty/vendor/google/aosp from branch 'master'
  to a73b5709dc716fa17e68e00a863e05f4bebdc4d7
  - Add Rust host library path
    
    To build Rust crates for proc macros, we need to link against the Rust
    host libraries in prebuilts. Adds the path to the current version of
    these libraries to the build environment.
    
    Test: build.py
    Bug: 229156386
    Change-Id: I3e52b25fb463a0788700466994a1b29b29f75793
    
diff --git a/external/lk b/external/lk
index c37cf14..5247c42 160000
--- a/external/lk
+++ b/external/lk
@@ -1 +1 @@
-Subproject commit c37cf14fceb065e0e222cbd813b024b005233861
+Subproject commit 5247c42ccc94917d1423104abbc7ae8330ebab40
diff --git a/trusty/kernel b/trusty/kernel
index 3a12d34..e7c4b8c 160000
--- a/trusty/kernel
+++ b/trusty/kernel
@@ -1 +1 @@
-Subproject commit 3a12d346c921eeb74c0d55747f45b5cf322a8364
+Subproject commit e7c4b8c3f08695467f175b848ce4891c0bd3f0d6
diff --git a/trusty/user/base b/trusty/user/base
index 3866c9d..87be052 160000
--- a/trusty/user/base
+++ b/trusty/user/base
@@ -1 +1 @@
-Subproject commit 3866c9dc9869a601d205613e484c09bcfbb1216d
+Subproject commit 87be0526167ab63316b9b27962a0b81b336c65aa
diff --git a/trusty/vendor/google/aosp b/trusty/vendor/google/aosp
index 724047b..a73b570 160000
--- a/trusty/vendor/google/aosp
+++ b/trusty/vendor/google/aosp
@@ -1 +1 @@
-Subproject commit 724047b0dda8083557987fcde2ccc4f586b2bfc7
+Subproject commit a73b5709dc716fa17e68e00a863e05f4bebdc4d7