Ada can't export an entity more than once, but the linker might be able to create aliases, for GNAT/GCC this works (at least on my laptop):

1.multiple_exports.txt

Build instructions:

> gcc -c foobar.c -o foobar.o
> gnatmake multiple_exports-main.adb -largs foobar.o -Wl,--defsym=baz_ada=bar_ada,--defsym=qux_ada=bar_ada

foobar.c

extern void bar_ada(int);
extern void baz_ada(int);
extern void qux_ada(int);

void foobar_c()
{
   bar_ada(1337);
   baz_ada(42);
   qux_ada(420);
}

multiple_exports-main.adb

procedure Multiple_Exports.Main 
is
   procedure Foobar 
      with Import, 
         Convention => C, 
         External_Name => "foobar_c";
begin
   Foobar;
end Multiple_Exports.Main;

multiple_exports.adb

with Ada.Text_IO;

package body Multiple_Exports is

   procedure Bar( P : Interfaces.C.int )
   is
   begin
      Ada.Text_IO.Put_Line("Bar" & P'Image);
   end Bar;

end Multiple_Exports;

multiple_exports.ads

with Interfaces.C;

package Multiple_Exports is
   
   procedure Bar( P : Interfaces.C.int )
      with Export, 
         Convention => C, 
         External_Name => "bar_ada";

end Multiple_Exports;