Add build instructions. Improve build.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

README

@@ -9,6 +9,18 @@ Requirements:
 - cmake
   http://www.cmake.org
 
+Instructions for DEBUG build 
+  mkdir -p build/debug
+  cd build/debug
+  cmake -DCMAKE_BUILD_TYPE=DEBUG ../../src        
+  make
+
+Instructions for RELEASE build 
+  mkdir -p build/release
+  cd build/release
+  cmake -DCMAKE_BUILD_TYPE=RELEASE ../../src        
+  make
+
 Instructions for installing gcc-4.8 (C++11 compatible) on Ubuntu
 Execute:
     sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y

src/CMakeLists.txt

@@ -2,11 +2,43 @@ cmake_minimum_required (VERSION 2.8.7)
 project (LEAN CXX)
 set (LEAN_VERSION_MAJOR 0)
 set (LEAN_VERSION_MINOR 1)
-set (CMAKE_CXX_COMPILER "g++-4.8")
-set (CMAKE_CXX_FLAGS_DEBUG "-DLEAN_DEBUG -DLEAN_TRACE -g")
-set (CMAKE_CXX_FLAGS_RELEASE "-O3")
+
 set (CMAKE_COLOR_MAKEFILE ON)
-add_definitions(-std=c++11 -Wall)
+
+# Initialize CXXFLAGS.
+set(CMAKE_CXX_FLAGS                "-Wall -std=c++11")
+set(CMAKE_CXX_FLAGS_DEBUG          "-O0 -g -DLEAN_DEBUG -DLEAN_TRACE")
+set(CMAKE_CXX_FLAGS_MINSIZEREL     "-Os -DNDEBUG")
+set(CMAKE_CXX_FLAGS_RELEASE        "-O3 -DNDEBUG")
+set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -g")
+
+# Compiler-specific C++11 activation.
+if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
+    execute_process(
+        COMMAND ${CMAKE_CXX_COMPILER} -dumpversion OUTPUT_VARIABLE GCC_VERSION)
+    if (NOT (GCC_VERSION VERSION_GREATER 4.8 OR GCC_VERSION VERSION_EQUAL 4.8))
+        message(FATAL_ERROR "${PROJECT_NAME} requires g++ 4.8 or greater.")
+    endif ()
+elseif ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
+else ()
+    message(FATAL_ERROR "Your C++ compiler does not support C++11.")
+endif ()
+
+if (GMP_INCLUDE_DIR AND GMP_LIBRARIES)
+   # Already in cache, be silent
+   set(GMP_FIND_QUIETLY TRUE)
+endif (GMP_INCLUDE_DIR AND GMP_LIBRARIES)
+
+find_path(GMP_INCLUDE_DIR NAMES gmp.h )
+find_library(GMP_LIBRARIES NAMES gmp libgmp )
+MESSAGE(STATUS "GMP: " ${GMP_LIBRARIES})
+
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(GMP DEFAULT_MSG GMP_INCLUDE_DIR GMP_LIBRARIES)
+mark_as_advanced(GMP_INCLUDE_DIR GMP_LIBRARIES)
+
+set (CMAKE_CXX_COMPILER "g++-4.8")
 
 add_subdirectory(util)
 add_subdirectory(shell)

src/shell/CMakeLists.txt

@@ -6,7 +6,7 @@ configure_file (
 include_directories("${LEAN_BINARY_DIR}")
 
 include_directories (${LEAN_SOURCE_DIR}/util) 
-set (EXTRA_LIBS ${EXTRA_LIBS} util gmp)
+set (EXTRA_LIBS ${EXTRA_LIBS} util ${GMP_LIBRARIES})
 
 add_executable(lean lean.cpp)
 target_link_libraries (lean ${EXTRA_LIBS})