Allow the user to set build flags

Author: asarhaddon

lib/gnat/aunit.gpr

@@ -27,6 +27,13 @@ project AUnit is
    for Library_Version use
      external ("AUNIT_LIBRARY_VERSION", "libaunit.so.0.0");
 
+   case AUnit_Shared.Library_Kind is
+      when "dynamic" | "relocatable" =>
+         --  Put options like --as-needed before the libraries.
+         for Leading_Library_Options use external_As_List ("LDFLAGS", " ");
+      when others =>
+   end case;
+
    --------------
    -- Compiler --
    --------------
@@ -43,6 +50,10 @@ project AUnit is
               ("-O2", "-gnatp", "-gnatn", "-gnatwa.X");
       end case;
 
+      --  Allow user flags to override default flags.
+      for Default_Switches ("ada") use
+        Compiler'Default_Switches ("ada") & external_As_List ("ADAFLAGS", " ");
+
       for Switches ("aunit.adb") use
         Compiler'Default_Switches ("ada") & ("-fno-strict-aliasing");
    end Compiler;