Document raised CMake requirement

We raised the requirement in cb3c78f but forgot to update the
documentation.

diff --git a/BUILDING.txt b/BUILDING.txt
index d996d448351208b42eda2c436eca69890cea3d63..9754796b0b18bdca17f9b2fc623608d94f137cb7 100644 (file)
--- a/BUILDING.txt
+++ b/BUILDING.txt
@@ -7,7 +7,7 @@
 Build Requirements (All Systems)
 ================================
 
--- CMake (http://www.cmake.org) v2.8 or later
+-- CMake (http://www.cmake.org) v3.10 or later
 
 -- zlib