Conflicting library definitions for __mpu_init() when using Clang compiler

When using the static libraries created by the PDK (make pdk_libs), the ti.csl.init.aer5f library contains a definition for __mpu_init() when build for the R5F cores. The library libc.a from the Clang compiler also contains a definition for __mpu_init().

Currently, unless the order of the library inclusion has the ti.csl.init.aer5f first in the linker command, another library might (very possibly) pull in libc.a before ti.csl.init.aer5f.

Current fix:

1) Ensure ti.csl.init.aer5f is the first library included in the linker command.

2) Use the --priority flag for the linker to ensure that the function is pulled from ti.csl.init.aer5f

Possible bugs:

• If the libc.a is needed before the __mpu_init() call, libc.a might still be pulled in before ti.csl.init.aer5f is even linked
• IF other libraries experience a similar conflict with libc.a (or any other RTS lib), there could be a deadlock where one library won't be able to be linked before libc.a