Add documentation to tool chains

hopefully make it easier to install

README.md

@@ -31,8 +31,12 @@ As an example here is an `initial_config.cmake` file used to construct `sisso++`
 ###############
 set(CMAKE_CXX_COMPILER g++ CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-O2" CACHE STRING "")
-set(EXTERNAL_BOOST OFF CACHE BOOL "")
+
+#################
+# Feature Flags #
+#################
 set(USE_PYTHON ON CACHE BOOL "")
+set(EXTERNAL_BOOST OFF CACHE BOOL "")
 ```
 Here the `-O2` flag is for optimizations, it is recommended to stay as `-O2` or `-O3`, but it can be changed to match compiler requirements.
 

cmake/toolchains/gnu_no_py.cmake

@@ -3,5 +3,9 @@
 ###############
 set(CMAKE_CXX_COMPILER g++ CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-O2" CACHE STRING "")
+
+#################
+# Feature Flags #
+#################
 set(USE_PYTHON OFF CACHE BOOL "")
 set(EXTERNAL_BOOST OFF CACHE BOOL "")

cmake/toolchains/gnu_py.cmake

@@ -3,5 +3,9 @@
 ###############
 set(CMAKE_CXX_COMPILER g++ CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-O2" CACHE STRING "")
+
+#################
+# Feature Flags #
+#################
 set(USE_PYTHON ON CACHE BOOL "")
 set(EXTERNAL_BOOST OFF CACHE BOOL "")

cmake/toolchains/intel_no_py.cmake

@@ -3,5 +3,9 @@
 ###############
 set(CMAKE_CXX_COMPILER icpc CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-O3" CACHE STRING "")
-set(USE_PYTHON OFF CACHE BOOL "")
 
+#################
+# Feature Flags #
+#################
+set(USE_PYTHON OFF CACHE BOOL "")
+set(EXTERNAL_BOOST OFF CACHE BOOL "")

cmake/toolchains/intel_py.cmake

@@ -3,5 +3,9 @@
 ###############
 set(CMAKE_CXX_COMPILER icpc CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-O3" CACHE STRING "")
-set(USE_PYTHON ON CACHE BOOL "")
 
+#################
+# Feature Flags #
+#################
+set(USE_PYTHON ON CACHE BOOL "")
+set(EXTERNAL_BOOST OFF CACHE BOOL "")