support: allow override of ADAFLAGS, LDFLAGS, library shared object version

Author: asarhaddon

support/langkit_support.gpr

@@ -12,6 +12,14 @@ library project Langkit_Support is
    Library_Kind_Param : Library_Kind_Type := external
      ("LIBRARY_TYPE", external ("LANGKIT_SUPPORT_LIBRARY_TYPE", "static"));
 
+   type OS_Kind is ("windows", "unix", "osx");
+   OS : OS_Kind := External ("LANGKIT_SUPPORT_OS", "windows");
+
+   Soversion := External ("LANGKIT_SUPPORT_SOVERSION", "1");
+
+   Adaflags  := External_As_List ("ADAFLAGS", " ");
+   Ldflags   := External_As_List ("LDFLAGS", " ");
+
    for Languages use ("Ada");
    for Source_Dirs use (".");
    for Object_Dir use "obj/" & Build_Mode;
@@ -70,20 +78,35 @@ library project Langkit_Support is
 
    for Library_Dir use "lib/" & Library_Kind_Param & "/" & Build_Mode;
 
+   So_Ext := "";
+   case OS is
+      when "windows" => So_Ext := "dll";
+      when "osx"     => So_Ext := "dylib";
+      when "unix"    => So_Ext := "so";
+   end case;
+
+   case Library_Kind_Param is
+      when "relocatable" =>
+         for Library_version use "lib" & project'Library_Name & "." & So_Ext
+                                 & "." & Soversion;
+         for Leading_Library_Options use Ldflags;
+      when "static" | "static-pic" =>
+         null;
+   end case;
+
    Common_Ada_Cargs := ("-gnatwa", "-gnatyg", "-fPIC");
 
    package Compiler is
+      Mode_Args := ();
       case Build_Mode is
          when "dev" =>
-            for Default_Switches ("Ada") use
-               Common_Ada_Cargs & ("-g", "-O0", "-gnatwe", "-gnata");
-
+            Mode_Args := ("-g", "-O0", "-gnatwe", "-gnata");
          when "prod" =>
             --  Debug information is useful even with optimization for
             --  profiling, for instance.
-            for Default_Switches ("Ada") use
-               Common_Ada_Cargs & ("-g", "-Ofast");
+            Mode_Args := ("-g", "-Ofast");
       end case;
+      for Default_Switches ("Ada") use Common_Ada_Cargs & Mode_Args & Adaflags;
    end Compiler;
 
 end Langkit_Support;