Fix sandbox build by setting /tmp --syslibdir during musl build

Test Plan: Ran a clean `scripts:launch` build, no longer failed.

X-Origin-Diff: phab/D205
GitOrigin-RevId: 6edd31d46816414c6b4c51664f23ce9d7c6d603d
diff --git a/build/utils/BUILD b/build/utils/BUILD
index 0a3454b..d1abdd4 100644
--- a/build/utils/BUILD
+++ b/build/utils/BUILD
@@ -38,7 +38,7 @@
     echo "Compiling and installing musl..."
     (
         cd external/musl
-        ./configure --prefix=$$MUSL
+        ./configure --prefix=$$MUSL --syslibdir=$$MUSL/lib
         make -j 8 install
     ) > /dev/null