Trying to build latest branch and hitting a compile error

Hello Team

I am trying to follow the docs found [here](https://github.com/iovisor/bcc/blob/master/INSTALL.md#ubuntu---source)

My current environment is :
```
$ uname -a
Linux ymo-dt1 4.15.0-96-generic #97-Ubuntu SMP Wed Apr 1 03:25:46 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.4 LTS
Release: 18.04
Codename: bionic
```

I checked out the latest branch on master and i am getting this compile error:
```
+ cmake .. -DCMAKE_INSTALL_PREFIX=/src/ebpf/bcc-master-dist
-- Latest recognized Git tag is v0.14.0
-- Git HEAD is d2e8ea47352e36f63a9dda281c00fadeb87e890a
-- Revision is 0.14.0-d2e8ea47
-- Found LLVM: /usr/lib/llvm-6.0/include 6.0.0
-- Using static-libstdc++
-- Could NOT find LuaJIT (missing: LUAJIT_LIBRARIES LUAJIT_INCLUDE_DIR)
CMake Warning at tests/python/CMakeLists.txt:10 (message):
Recommended test program 'netperf' not found

CMake Warning at tests/python/CMakeLists.txt:16 (message):
Recommended test program 'iperf' or 'iperf3' not found

-- Configuring done
-- Generating done
-- Build files have been written to: /src/ebpf/bcc-master/build
[ 1%] Building CXX object src/cc/frontends/clang/CMakeFiles/clang_frontend.dir/b_frontend_action.cc.o
In file included from /usr/lib/llvm-6.0/include/clang/AST/RecursiveASTVisitor.h:24:0,
from /src/ebpf/bcc-master/src/cc/frontends/clang/b_frontend_action.h:23,
from /src/ebpf/bcc-master/src/cc/frontends/clang/b_frontend_action.cc:31:
/usr/lib/llvm-6.0/include/clang/AST/DeclOpenMP.h:97:1: warning: multi-line comment [-Wcomment]
/// #pragma omp declare reduction (foo : int,float : omp_out += omp_in) \
^
/src/ebpf/bcc-master/src/cc/frontends/clang/b_frontend_action.cc: In member function ‘bool ebpf::BTypeVisitor::VisitVarDecl(clang::VarDecl*)’:
/src/ebpf/bcc-master/src/cc/frontends/clang/b_frontend_action.cc:1295:18: error: ‘BPF_MAP_TYPE_SK_STORAGE’ was not declared in this scope
map_type = BPF_MAP_TYPE_SK_STORAGE;
^~~~~~~~~~~~~~~~~~~~~~~
/src/ebpf/bcc-master/src/cc/frontends/clang/b_frontend_action.cc:1295:18: note: suggested alternative: ‘BPF_MAP_TYPE_CGROUP_STORAGE’
map_type = BPF_MAP_TYPE_SK_STORAGE;
^~~~~~~~~~~~~~~~~~~~~~~
BPF_MAP_TYPE_CGROUP_STORAGE
src/cc/frontends/clang/CMakeFiles/clang_frontend.dir/build.make:95: recipe for target 'src/cc/frontends/clang/CMakeFiles/clang_frontend.dir/b_frontend_action.cc.o' failed
make[2]: *** [src/cc/frontends/clang/CMakeFiles/clang_frontend.dir/b_frontend_action.cc.o] Error 1
CMakeFiles/Makefile2:1001: recipe for target 'src/cc/frontends/clang/CMakeFiles/clang_frontend.dir/all' failed
make[1]: *** [src/cc/frontends/clang/CMakeFiles/clang_frontend.dir/all] Error 2
Makefile:160: recipe for target 'all' failed
make: *** [all] Error 2
```