Change the default based on being a git clone

This does what had been done by hand in the past, check for .git in the
source directory, if present keep the default as Debug otherwise switch
it to Release.

Signed-off-by: Marcus D. Hanwell <mhanwell@bnl.gov>

cmake/BuildType.cmake

@@ -1,7 +1,12 @@
 # Set a default build type if none was specified
+set(_build_type "Release")
+if(EXISTS "${CMAKE_SOURCE_DIR}/.git")
+  set(_build_type "Debug")
+endif()
 if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
-  message(STATUS "Setting build type to 'Debug' as none was specified.")
-  set(CMAKE_BUILD_TYPE Debug CACHE STRING "Choose the type of build." FORCE)
+  message(STATUS "Setting build type to '${_build_type}' as none was specified.")
+  set(CMAKE_BUILD_TYPE ${_build_type}
+      CACHE STRING "Choose the type of build." FORCE)
   # Set the possible values of build type for cmake-gui
   set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release"
     "MinSizeRel" "RelWithDebInfo" "ASAN" "TSAN" "MSAN" "LSAN" "UBSAN")