readme: add howto for ubuntu (tpruvot#23)

tested on 17.10

README.md

@@ -1,5 +1,4 @@
-ccminer
-=======
+# ccminer
 
 Based on Christian Buchner's & Christian H.'s CUDA project, no more active on github since 2014.
 
@@ -22,15 +21,36 @@ About source code dependencies
 This project requires some libraries to be built :
 
 - OpenSSL (prebuilt for win)
-
 - Curl (prebuilt for win)
-
 - pthreads (prebuilt for win)
 
 The tree now contains recent prebuilt openssl and curl .lib for both x86 and x64 platforms (windows).
 
 To rebuild them, you need to clone this repository and its submodules :
     git clone https://github.com/peters/curl-for-windows.git compat/curl-for-windows
 
-On Linux, you can use the helper ./build.sh (edit configure.sh and the Makefile.am if required)
 
+# Linux
+
+## Ubuntu
+
+Install dependencies
+```sudo apt-get install git libcurl4-openssl-dev nvidia-cuda-toolkit build-essential```
+
+Ubuntu is shipped with Gcc 7 so install Gcc 5 and make it the default
+
+```
+sudo apt-get install gcc-5 g++-5
+sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 1
+```
+Clone code
+```
+git clone https://github.com/tpruvot/ccminer.git
+cd ccminer
+```
+
+Use the helper ./build.sh  (edit configure.sh and the Makefile.am if required)
+```
+./build.sh
+./ccminer --version
+```