Remove glibc-2.15

All uses of glibc 2.15 were replaced over a week ago. Everything appears
to be running along smoothly at this point, so we can now remove the
old.

Bug: 111358231
Test: repo sync && lunch aosp_marlin-eng && m (same on internal master,
      s/aosp_marlin-eng/marlin-eng/`)

Change-Id: I0f862f759b6ff716c6dc60252ef8f52db2bf16b7
diff --git a/default.xml b/default.xml
index 5f914d2..386dbe8 100644
--- a/default.xml
+++ b/default.xml
@@ -622,7 +622,6 @@
   <project path="prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.9" name="platform/prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.9" groups="pdk,darwin,x86" clone-depth="1" />
   <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="pdk,linux,arm" clone-depth="1" />
   <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="pdk,linux,arm" clone-depth="1" />
-  <project path="prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.15-4.8" name="platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.15-4.8" groups="pdk,linux" clone-depth="1" />
   <project path="prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8" name="platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8" groups="pdk,linux" clone-depth="1" />
   <project path="prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8" name="platform/prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8" groups="pdk-fs" clone-depth="1" />
   <project path="prebuilts/gcc/linux-x86/mips/mips64el-linux-android-4.9" name="platform/prebuilts/gcc/linux-x86/mips/mips64el-linux-android-4.9" groups="pdk,linux,mips" clone-depth="1" />