vagrant: dynamic link bcc against llvm

When static linking LLVM into bcc we run into issues:

```
: CommandLine Error: Option 'help-list' registered more than once!
LLVM ERROR: inconsistency in registered CommandLine options
Aborted (core dumped)
```

There might be a smart way to fix this in cmake, maybe just specifying
 bcc before llvm on the linker cli, but this is easier atm.

Vagrantfile

@@ -28,7 +28,8 @@ mkdir -p bcc/build
 cd bcc/build
 git checkout v0.19.0
 cmake .. -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=/usr/local \
-  -DENABLE_EXAMPLES=0 -DENABLE_TESTS=0 -DENABLE_MAN=0
+  -DENABLE_EXAMPLES=0 -DENABLE_TESTS=0 -DENABLE_MAN=0 \
+  -DENABLE_LLVM_SHARED=1
 make && sudo make install && sudo ldconfig
 EOF