Fix linking of bc7, needs symbols from nvmath

If nvtt is build with -Wl,--as-needed, the linker will not resolve bc7
symbols from any library listed earlier, make sure it (also) appears
after libbc7.a

src/bc7/CMakeLists.txt

@@ -23,6 +23,8 @@ SET(BC7_SRCS
 
 ADD_LIBRARY(bc7 STATIC ${BC7_SRCS})
 
+TARGET_LINK_LIBRARIES(bc7 nvmath)
+
 IF(NOT WIN32)
     IF(CMAKE_COMPILER_IS_GNUCXX)
         SET_TARGET_PROPERTIES(bc7 PROPERTIES COMPILE_FLAGS -fPIC)