Fix revision for prebuilts/clang/host/linux-x86

It should match the default for other projects (which is master).
diff --git a/default.xml b/default.xml
index cc62e82..2ac913f 100644
--- a/default.xml
+++ b/default.xml
@@ -135,7 +135,7 @@
   <project path="hardware/libhardware_legacy" name="platform/hardware/libhardware_legacy" groups="bdk" />
   <project path="libnativehelper" name="platform/libnativehelper" groups="bdk" />
   <project path="prebuilts/android-emulator" name="platform/prebuilts/android-emulator" clone-depth="1" groups="bdk" />
-  <project path="prebuilts/clang/host/linux-x86" name="platform/prebuilts/clang/host/linux-x86" revision="master" clone-depth="1" groups="linux,bdk" />
+  <project path="prebuilts/clang/host/linux-x86" name="platform/prebuilts/clang/host/linux-x86" clone-depth="1" groups="linux,bdk" />
   <project path="prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9" name="platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9" groups="linux,arm,bdk" />
   <project path="prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9" name="platform/prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9" groups="linux,arm,bdk" />
   <project path="prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.8" name="platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.11-4.8" groups="linux,bdk" />