Loosened the restriction to always require GMP a bit.

Former-commit-id: 0537ff217a

CMakeLists.txt

@@ -341,7 +341,9 @@ if(GMP_FOUND)
 elseif(MPIR_FOUND)
 	link_directories(${GMP_MPIR_LIBRARY_DIR} ${GMP_MPIRXX_LIBRARY_DIR})
 else(GMP_FOUND)
-	message(FATAL_ERROR "GMP is required for MathSAT, but was not found!")
+    if (ENABLE_MSAT)
+        message(FATAL_ERROR "GMP is required for MathSAT, but was not found!")
+    endif(ENABLE_MSAT)
 endif(GMP_FOUND)
 
 if ((NOT Boost_LIBRARY_DIRS) OR ("${Boost_LIBRARY_DIRS}" STREQUAL ""))