Does not build on any platform other than i386/amd64

I recently packaged MariaDB Connector/ODBC for Debian, see https://tracker.debian.org/pkg/mariadb-connector-odbc . After uploading it turned out that it fails to build on any platform that is not amd64 (x86_64) or i386.

https://buildd.debian.org/status/package.php?p=mariadb-connector-odbc

It fails to build on any other platform with

-- Looking for floor

-- Looking for floor - not found

-- Looking for floor in m

-- Looking for floor in m - found

-- odbc_config is not found 

-- Found ODBC Driver Manager includes: /usr/include

CMake Error at CMakeLists.txt:237 (MESSAGE):

  Driver Manager was not found

There is a lot of debug output from CMake after that, but I think those all come from the libm tests that passed before. Looking at cmake/FindDM.cmake I think it can work on any other platform right now, because it i.e. hardcodes the library path to x86_64-linux-gnu on all 64bit platforms.