fix(makemaker): write Build proxy when Build.PL is present

src/main/java/org/perlonjava/core/Configuration.java

@@ -33,7 +33,7 @@ public final class Configuration {
      * Automatically populated by Gradle/Maven during build.
      * DO NOT EDIT MANUALLY - this value is replaced at build time.
      */
-    public static final String gitCommitId = "e3750ee00";
+    public static final String gitCommitId = "00acf915b";
 
     /**
      * Git commit date of the build (ISO format: YYYY-MM-DD).
@@ -48,7 +48,7 @@ public final class Configuration {
      * Parsed by App::perlbrew and other tools via: perl -V | grep "Compiled at"
      * DO NOT EDIT MANUALLY - this value is replaced at build time.
      */
-    public static final String buildTimestamp = "Apr 28 2026 13:11:57";
+    public static final String buildTimestamp = "Apr 28 2026 13:54:08";
 
     // Prevent instantiation
     private Configuration() {

src/main/perl/lib/ExtUtils/MakeMaker.pm

@@ -339,6 +339,7 @@ sub _install_pure_perl {
         my $mm = PerlOnJava::MM::Installed->new($args);
         _create_mymeta($name, $version, $args);
         _create_install_makefile($name, $version, $args, {}, {}, $mm);
+        _create_build_script_proxy() if -f 'Build.PL';
         return $mm;
     }
 
@@ -398,6 +399,15 @@ sub _install_pure_perl {
 
     # Create Makefile with install commands (actual install deferred to 'make')
     _create_install_makefile($name, $version, $args, \%pm, \%scripts, $mm);
+
+    # If Build.PL exists in cwd, the distribution was configured via Module::Build
+    # (or Module::Install's Build.PL-delegates-to-Makefile.PL trick). CPAN.pm will
+    # then invoke `./Build`, `./Build test`, `./Build install` instead of `make`.
+    # Write a thin Build script that delegates to the corresponding make targets,
+    # so the Module::Build flow works on top of our Makefile.
+    if (-f 'Build.PL') {
+        _create_build_script_proxy();
+    }
 
     my $total = scalar(keys %pm) + scalar(keys %scripts);
     print "=" x 60, "\n";
@@ -738,6 +748,50 @@ sub _shell_cp {
     return "\t\@if [ -f '$src' ]; then rm -f '$dest' && cp '$src' '$dest'; else echo 'PerlOnJava: skipping missing source: $src'; fi";
 }
 
+# Write a tiny `Build` script that delegates to make targets. Some CPAN
+# distributions ship a Build.PL whose only job is to delegate to Makefile.PL
+# (Module::Install's "Dear Distribution Packager" trick, e.g. Data::Utilities).
+# CPAN.pm sees Build.PL, sets $self->{modulebuild} = 1, and then expects to
+# invoke `./Build`, `./Build test`, `./Build install`. Without a real
+# Module::Build (which we don't run here because PerlOnJava MakeMaker took
+# over WriteMakefile via Makefile.PL), no Build script is produced and the
+# CPAN install fails with "no Build file available". This proxy bridges the
+# gap by translating Module::Build subcommands to the corresponding make
+# targets generated by _create_install_makefile.
+sub _create_build_script_proxy {
+    my $build = 'Build';
+    open my $fh, '>', $build or do {
+        warn "Note: Could not create Build script: $!\n";
+        return;
+    };
+    print $fh <<'BUILD';
+#!/usr/bin/env perl
+# Generated by PerlOnJava MakeMaker as a Module::Build->make proxy.
+# CPAN.pm runs this when a Build.PL was used to configure the dist.
+use strict;
+use warnings;
+my $cmd  = shift @ARGV;
+$cmd = 'all' if !defined $cmd || $cmd eq '' || $cmd eq 'build';
+# Map Module::Build subcommands to make targets. Anything unknown is
+# passed through verbatim so e.g. './Build distclean' still works.
+my %map = (
+    all       => 'all',
+    test      => 'test',
+    install   => 'install',
+    clean     => 'clean',
+    realclean => 'realclean',
+    distclean => 'distclean',
+    config    => 'config',
+);
+my $target = exists $map{$cmd} ? $map{$cmd} : $cmd;
+my @make = ($ENV{MAKE} || 'make', $target, @ARGV);
+exec { $make[0] } @make
+    or die "PerlOnJava Build proxy: failed to exec '@make': $!\n";
+BUILD
+    close $fh;
+    chmod 0755, $build;
+}
+
 sub _create_mymeta {
     my ($name, $version, $args) = @_;