[Ada] New routine to access file on command line

This patch adds a new routine to query the first file argument of the
commandline without moving to the next file. This is needed in SPARK.

There is no impact on compilation.

2019-07-03  Johannes Kanig  <kanig@adacore.com>

gcc/ada/

	* osint.ads, osint.adb (Get_First_Main_File_Name): New routine
	to access the first file provided on the command line.

From-SVN: r272984

gcc/ada/ChangeLog

+2019-07-03  Johannes Kanig  <kanig@adacore.com>
+
+	* osint.ads, osint.adb (Get_First_Main_File_Name): New routine
+	to access the first file provided on the command line.
+
 2019-07-03  Ed Schonberg  <schonberg@adacore.com>
 
 	* inline.adb (Process_Formals_In_Aspects): New procedure within

gcc/ada/osint.adb

@@ -1422,6 +1422,15 @@ package body Osint is
       return Name_Find;
    end Get_Directory;
 
+   ------------------------------
+   -- Get_First_Main_File_Name --
+   ------------------------------
+
+   function Get_First_Main_File_Name return String is
+   begin
+      return File_Names (1).all;
+   end Get_First_Main_File_Name;
+
    --------------------------
    -- Get_Next_Dir_In_Path --
    --------------------------

gcc/ada/osint.ads

@@ -511,6 +511,9 @@ package Osint is
    procedure Dump_Command_Line_Source_File_Names;
    --  Prints out the names of all source files on the command-line
 
+   function Get_First_Main_File_Name return String;
+   --  Return the file name of the first main file
+
    -------------------------------------------
    -- Representation of Library Information --
    -------------------------------------------