Add a SPARK Main template

resources/templates/spark_main/example.yaml

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+name: SPARK Main
+description: Simple overrideable provable main
+main: main

resources/templates/spark_main/main.adb

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+procedure Main is
+begin
+   null;
+end Main;

resources/templates/spark_main/main.adc

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+
+pragma Profile(GNAT_Extended_Ravenscar);
+pragma Partition_Elaboration_Policy(Sequential);
+pragma SPARK_Mode (On);
+pragma Warnings (Off, "no Global contract available");
+pragma Warnings (Off, "subprogram * has no effect");

resources/templates/spark_main/main.gpr

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+project Main is
+
+   for Main use ("main.adb");
+
+   package Compiler is
+      for Switches ("ada") use ("-g", "-gnatwa", "-gnatQ");
+   end Compiler;
+
+   package Builder is
+      for Switches ("ada") use ("-g", "-O0");
+
+      for Global_Configuration_Pragmas use "main.adc";
+   end Builder;
+
+end Main;