[lmi] Inchoate support for GNU/Linux builds with lmi makefiles

[Greg Chicares]

It had become too painful to try to test numerical subtleties
with a single compiler on a single architecture...so, after
commit ae5c2adbb361b4962458919f497012e9d734ab07...

/home/greg[0]$schroot --chroot=cross-lmi                          
/home/greg[0]$unset LMI_HOST
/home/greg[0]$cd /opt/lmi/src/lmi
/opt/lmi/src/lmi[0]$make $coefficiency build_type=native CXXFLAGS='-O2 -ggdb 
-m64 -Wno-pedantic' CFLAGS='-m64' LDFLAGS='-m64' unit_tests 
unit_test_targets=bourn_cast_test             
make[2]: Nothing to be done for 'build_unit_tests'.
List of unit-test targets that did not build successfully:

List ends.

Running bourn_cast_test:

  Speed tests (Double, Float, Signed, Unsigned):

  static_cast<U>(S): 3.207e-04 s =     320650 ns, mean of 100 iterations
   bourn_cast<U>(S): 3.180e-04 s =     317970 ns, mean of 100 iterations
   bourn_cast<S>(U): 3.247e-04 s =     324650 ns, mean of 100 iterations

  static_cast<D>(U): 5.534e-04 s =     553360 ns, mean of 100 iterations
   bourn_cast<D>(U): 9.403e-04 s =     940280 ns, mean of 100 iterations

  static_cast<U>(D): 1.839e-03 s =    1838520 ns, mean of 100 iterations
   bourn_cast<U>(D): 5.146e-03 s =    5145600 ns, mean of 100 iterations
   bourn_cast<S>(D): 4.697e-03 s =    4696770 ns, mean of 100 iterations

  static_cast<F>(D): 1.541e-03 s =    1541080 ns, mean of 100 iterations
   bourn_cast<F>(D): 2.849e-03 s =    2849210 ns, mean of 100 iterations
   bourn_cast<D>(F): 3.027e-03 s =    3026800 ns, mean of 100 iterations

.... 540 tests succeeded

!!!! no errors detected