llvm 3.7+ deb is broken

https://llvm.org/bugs/show_bug.cgi?id=24154

Build from source until it's resolved. Another plan is to provide
binary package.
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>

INSTALL.md

-# Ubuntu - Docker edition
-
-The build dependencies are captured in a [Dockerfile](Dockerfile.ubuntu), the
-output of which is a .deb for easy installation.
-
-* Start with a recent Ubuntu install (tested with 14.04 LTS)
-* Install a [>= 4.2 kernel](http://kernel.ubuntu.com/~kernel-ppa/mainline/)
-  with headers
-* Reboot
-* Install [docker](https://docs.docker.com/installation/ubuntulinux/)
-  (`wget -qO- https://get.docker.com/ | sh`)
-* Run the Dockerfile for Ubuntu - results in an installable .deb
-  * `git clone https://github.com/iovisor/bcc; cd bcc`
-  * `docker build -t bcc -f Dockerfile.ubuntu .`
-  * `docker run --rm -v /tmp:/mnt bcc sh -c "cp /root/bcc/build/*.deb /mnt"`
-  * `sudo dpkg -i /tmp/libbcc*.deb`
-* Run the example
-  * `sudo python /usr/share/bcc/examples/hello_world.py`
-
 # Fedora - Docker edition
 
 The build dependencies are captured in a [Dockerfile](Dockerfile.fedora), the
@@ -43,14 +24,16 @@ To build the toolchain from source, one needs:
 * Clang 3.7, built from the same tree as LLVM
 * cmake, gcc (>=4.7), flex, bison
 
-* Add the [LLVM binary repo](http://llvm.org/apt/) to your apt sources
-  * `echo "deb http://llvm.org/apt/trusty/ llvm-toolchain-trusty main" | sudo tee /etc/apt/sources.list.d/llvm.list`
-  * `wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -`
-  * `sudo apt-get update`
 * Install build dependencies
   * `sudo apt-get -y install bison build-essential cmake flex git libedit-dev python zlib1g-dev`
-* Install LLVM and Clang development libs
-  * `sudo apt-get -y install libllvm3.7 llvm-3.7-dev libclang-3.7-dev`
+* Build LLVM and Clang development libs
+  * `git clone http://llvm.org/git/llvm.git`
+  * `cd llvm/tools; git clone http://llvm.org/git/clang.git`
+  * `cd ..; mkdir -p build/install; cd build`
+  * `cmake -G "Unix Makefiles" -DLLVM_TARGETS_TO_BUILD="BPF" -DCMAKE_INSTALL_PREFIX=$PWD/install ..`
+  * `make -j4`
+  * `make install`
+  * `export PATH=$PWD/install/bin:$PATH`
 * Install and compile BCC
   * `git clone https://github.com/iovisor/bcc.git`
   * `mkdir bcc/build; cd bcc/build`