cmake: tweaks for EXAALT superbuild, add latte_fix

cmake/Modules/FindLATTE.cmake

@@ -0,0 +1,18 @@
+# - Find latte
+# Find the native LATTE libraries.
+#
+#  LATTE_LIBRARIES    - List of libraries when using fftw3.
+#  LATTE_FOUND        - True if fftw3 found.
+#
+
+find_library(LATTE_LIBRARY NAMES latte)
+
+set(LATTE_LIBRARIES ${LATTE_LIBRARY})
+
+include(FindPackageHandleStandardArgs)
+# handle the QUIETLY and REQUIRED arguments and set LATTE_FOUND to TRUE
+# if all listed variables are TRUE
+
+find_package_handle_standard_args(LATTE DEFAULT_MSG LATTE_LIBRARY)
+
+mark_as_advanced(LATTE_LIBRARY)