RTEMS/Ada: Define EH_MECHANISM

RTEMS/Ada: Define EH_MECHANISM

Without this definition I got the following error:

<...>/xgcc <...>  -c -g -O2   -W -Wall -gnatpg -nostdinc  -g -fno-inline \
      -fno-toplevel-reorder -O1  a-except.adb -o a-except.o
a-exexpr.adb:38:06: "System.Exceptions.Machine" is not a predefined library unit
a-exexpr.adb:38:06: "Ada.Exceptions (body)" depends on "Ada.Exceptions.Exception_Propagation (body)"
a-exexpr.adb:38:06: "Ada.Exceptions.Exception_Propagation (body)" depends on "System.Exceptions.Machine (spec)"
../gcc-interface/Makefile:2661: recipe for target 'a-except.o' failed

gcc/ada

	* gcc-interface/Makefile.in (RTEMS): Define EH_MECHANISM.

From-SVN: r255408