Roll garnet to b3ba6b6d6ab8ef658278cc43c9f839a8a8d1718e (flutter#4335)

* Roll garnet to b3ba6b6d6ab8ef658278cc43c9f839a8a8d1718e

Also includes a buildroot patch to pick up new dependency:
  build/config/fuchsia/sdk.gni

This fixes a build breakage in
garnet/public/lib/fxl/strings/string_view_unittest.cc wherein a variable
'sw5' was declared but the test erroneously tested against 'sw4' from
the previous test.

* Update license script for garnet

Reflects structural changes in directories we do not depend on. This
filters out the following directories in addition to what was already
filtered:
  garnet/drivers
  garnet/packages
  garnet/public/build/
  garnet/public/rust/

* Update licenses

DEPS

@@ -114,7 +114,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'a6e52dbb776c45cc8c57d7143b8eb8b2e762fdfb',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'a457e1429ed9e4a1869c8192b846bebb481f333a',
 
    # Fuchsia compatibility
    #
@@ -123,7 +123,7 @@ deps = {
    # and not have to specific specific hashes.
 
   'src/garnet':
-   Var('fuchsia_git') + '/garnet' + '@' + '73eeb0583e7967016ad7386a90353bf6937488b9',
+   Var('fuchsia_git') + '/garnet' + '@' + 'b3ba6b6d6ab8ef658278cc43c9f839a8a8d1718e',
 
   'src/topaz':
    Var('fuchsia_git') + '/topaz' + '@' + 'da66b94839f788a0bffc34fd9bdfef3360af8c18',

tools/licenses/lib/main.dart

@@ -2145,9 +2145,11 @@ class RepositoryGarnetDirectory extends RepositoryDirectory {
   bool shouldRecurse(fs.IoNode entry) {
     return entry.name != 'bin'
         && entry.name != 'docs'
+        && entry.name != 'drivers'
         && entry.name != 'examples'
         && entry.name != 'go'
         && entry.name != 'lib'
+        && entry.name != 'packages'
         && super.shouldRecurse(entry);
   }
 
@@ -2162,6 +2164,14 @@ class RepositoryGarnetDirectory extends RepositoryDirectory {
 class RepositoryGarnetPublicDirectory extends RepositoryDirectory {
   RepositoryGarnetPublicDirectory(RepositoryDirectory parent, fs.Directory io) : super(parent, io);
 
+  @override
+  bool shouldRecurse(fs.IoNode entry) {
+    return entry.name != 'dart-pkg'
+        && entry.name != 'build'
+        && entry.name != 'rust'
+        && super.shouldRecurse(entry);
+  }
+
   @override
   RepositoryDirectory createSubdirectory(fs.Directory entry) {
     if (entry.name == 'lib')
@@ -2175,7 +2185,9 @@ class RepositoryGarnetLibDirectory extends RepositoryDirectory {
 
   @override
   bool shouldRecurse(fs.IoNode entry) {
-    return entry.name != 'url'
+    return entry.name != 'app'
+        && entry.name != 'escher'
+        && entry.name != 'url'
         && super.shouldRecurse(entry);
   }