LLVM requires linking with the C++ compiler.

It's basically luck if it works with the C compiler on some platforms...
diff --git a/configs/linux-llvm b/configs/linux-llvm
index 8e9b408..b24959e 100644
--- a/configs/linux-llvm
+++ b/configs/linux-llvm
@@ -23,6 +23,7 @@
   LLVM_CXXFLAGS=`llvm-config --cxxflags` -DMESA_LLVM=1 -Wno-long-long
   LLVM_LDFLAGS=`llvm-config --ldflags`
   LLVM_LIBS=`llvm-config --libs`
+  MKLIB_OPTIONS=-cplusplus
 else
   LLVM_CFLAGS=
   LLVM_CXXFLAGS=