Don't use .perl in serialization ID creation

The source-line of 'use' statements is part of .perl output of
CompUnit::DependencySpecification, which was used to create serialization
ID's stored in .precomp files.  This adds a "serialization-id" method that
creates a shorter, but still readable string that is actually valid Raku
code, but does not contain the source-line number.  This should, possibly
drastically, reduce the number of attempts to load the same module.

src/core.c/CompUnit/DependencySpecification.pm6

@@ -12,6 +12,22 @@ class CompUnit::DependencySpecification {
           ($.auth-matcher   //True) ~~ Bool ?? '' !! ":auth<$.auth-matcher>",
           ($.api-matcher    //True) ~~ Bool ?? '' !! ":api<$.api-matcher>";
     }
+
+    # Provide an human readable *unique* serialization string that does *not*
+    # contain the line number in the source where it is invoked.
+    method serialize-id() {
+        my str $str = self.^name
+          ~ '.new(:short-name<'
+          ~ $.short-name
+          ~ '> :from<'
+          ~ $.from
+          ~ '>';
+        $str = $str ~ ' :!version-matcher' unless $.version-matcher;
+        $str = $str ~ ' :!auth-matcher'    unless $.auth-matcher;
+        $str = $str ~ ' :!api-matcher'     unless $.api-matcher;
+
+        $str ~ ')'
+    }
 }
 
 # vim: ft=perl6 expandtab sw=4

src/core.c/CompUnit/PrecompilationUnit.pm6

@@ -126,7 +126,7 @@ class CompUnit::PrecompilationDependency::File does CompUnit::PrecompilationDepe
         "$.id\0$.src\0$.checksum\0$specs"
 #?endif
 #?if !jvm
-        "$.id\0$.src\0$.checksum\0{$!serialized-spec ?? $!serialized-spec !! $!spec.perl}"
+        "$.id\0$.src\0$.checksum\0{$!serialized-spec ?? $!serialized-spec !! $!spec.serialize-id}"
 #?endif
     }