mingw: add x86_64-linux-glibc2.15-4.8 gcc prebuilt

Bug: b/73539603
Test: ./toolchain/mingw/build.sh (after updating script)
Change-Id: Ia0f59c3358b9be736fbacb13ebd9ee42a38fd2dc
diff --git a/default.xml b/default.xml
index b4f2c1c..d91c3cd 100644
--- a/default.xml
+++ b/default.xml
@@ -9,6 +9,7 @@
            sync-j="4" />
 
   <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="pdk,linux" />
+  <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" />
   <project path="toolchain/binutils" name="toolchain/binutils" />
   <project path="toolchain/cloog" name="toolchain/cloog" />
   <project path="toolchain/gcc" name="toolchain/gcc" />