ARM doesn't support the -m32/-m64 and as a result is FTBFS which indicates that R-RScaLAPACK isn't using the ditro specific compiler flags.
I don't know how that -m64 popped into the linker command string. You can see in the logs that the R-RScaLAPACK.spec is not passing it in anywhere.
The value for MPISHLIB_LD is evaluated from R_SHLIB_LD, which is R CMD config SHLIB_LD. You can see in the build log that R_SHLIB_LD does not include -m64, and that MPISHLIB_LD doesn't either.
The only place -m64 ever appears in the build logs is at that single linker invocation. I have no idea how to resolve this. If you had a prepped tree on the arm target, you might be able to grep it for the "-m64" string and see where it ends up getting added... that might shed some light on this.
This bug appears to have been reported against 'rawhide' during the Fedora 20 development cycle.
Changing version to '20'.
More information and reason for this action is here:
Package is retired and dead upstream