Allow the user to set build flags

Author: asarhaddon

lib/gnat/aunit.gpr

@@ -29,6 +29,8 @@ project AUnit is
       when "dynamic" | "relocatable" =>
          for Library_Kind use "relocatable";
          for Library_Version use AUnit_Shared.Library_Version;
+         --  Put options like --as-needed before the libraries.
+         for Leading_Library_Options use AUnit_Shared.Ldflags;
    end case;
 
    --------------
@@ -41,12 +43,15 @@ project AUnit is
             for Default_Switches ("ada") use
               ("-g", "-gnatQ", "-O1", "-gnatf", "-gnato",
                "-gnatwa.Xe", "-gnaty");
-
          when "Install" =>
             for Default_Switches ("ada") use
               ("-O2", "-gnatp", "-gnatn", "-gnatwa.X");
       end case;
 
+      --  Allow user flags to override default flags.
+      for Default_Switches ("ada") use
+        Compiler'Default_Switches ("ada") & AUnit_Shared.Adaflags;
+
       for Switches ("aunit.adb") use
         Compiler'Default_Switches ("ada") & ("-fno-strict-aliasing");
    end Compiler;

lib/gnat/aunit_shared.gpr

@@ -30,6 +30,9 @@ project AUnit_Shared is
    Library_Dir := External ("AUNIT_LIBDIR", "../aunit/" & Subdir);
    Object_Dir := External ("AUNIT_OBJDIR", "../aunit-obj/" & Subdir);
 
+   Adaflags := External_As_List ("ADAFLAGS", " ");
+   Ldflags := External_As_List ("LDFLAGS", " ");
+
    for Source_Dirs use ();
 
    type Exception_Type is ("fullexception", "certexception", "zfpexception");