fix(makemaker): mirror upstream prereq check (no false "have 0")

[fglock]

Summary

Fixes a misleading dependency-check report in PerlOnJava's ExtUtils::MakeMaker shim and aligns the prereq logic with upstream MakeMaker (Perl 5.42 / MakeMaker 7.76).

Problem

jcpan -t ACME::Error::Coy was printing a self-contradictory configure block:

PerlOnJava MakeMaker: ACME::Error::Coy v0.01
============================================================

Missing dependencies:
  - Coy (>= 0.01, have 0)

Please install these modules first.
(PerlOnJava uses bundled modules or pure Perl CPAN modules)


Will install to: /Users/fglock/.perlonjava/lib
  Coy.pm -> /Users/fglock/.perlonjava/lib/ACME/Error/Coy.pm

============================================================
Configured! 1 files will be installed when 'make install' runs.

Root cause: _check_prereqs did eval "require Coy; 1" and then read $Coy::VERSION. CPAN.pm sets PERL_USE_UNSAFE_INC=1 so . is on @INC. The cwd at configure time is the ACME-Error-Coy build directory, which contains a file literally named Coy.pm — but it declares package ACME::Error::Coy. require Coy happily loads the wrong file, %INC records Coy.pm, but $Coy::VERSION stays undef, so the check reports have 0. Coy is in fact not installed at all.

What real Perl does

System Perl's ExtUtils::MakeMaker (5.42, MakeMaker 7.76, lines ~579-647) does not require prereqs. It uses:

• MM->_installed_file_for_module($prereq) — file-path search of @INC for Foo/Bar.pm.
• MM->parse_version($installed_file) — static parse of $VERSION = ... from the file.

Reporting:

• File missing → warn "Warning: prerequisite Foo 1.0 not found.\n" and continue.
• Version too low → warn "Warning: prerequisite Foo 1.0 not found. We have 0.5.\n" and continue.
• MakeMaker FATAL: prerequisites not found.\n... Please install these modules first and rerun 'perl Makefile.PL'. — only on PREREQ_FATAL.

I confirmed system Perl on the same build dir is silent (parse_version returns 0.01 from the misnamed file, so the check looks satisfied; CPAN.pm independently catches the real missing dep via its own metadata).

Fix

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

• Add _installed_file_for_module mirroring upstream (skipping @INC code/array/blessed hooks).
• Rewrite _check_prereqs to use file-path search + MM->parse_version, never require.
• Emit per-module Warning: prerequisite Foo X not found. / ... We have Y. to STDERR with the upstream wording.
• Drop the unconditional Missing dependencies / Please install these modules first banner that contradicted the subsequent Configured! line.
• Honor PREREQ_FATAL and die with the upstream message.
• Aggregate BUILD_REQUIRES, CONFIGURE_REQUIRES, TEST_REQUIRES the same way upstream does.

After

$ jcpan -t ACME::Error::Coy
...
PerlOnJava MakeMaker: ACME::Error::Coy v0.01
Configured! 1 files will be installed when 'make install' runs.
PerlOnJava MakeMaker: Coy v0.06
Configured! 2 files will be installed when 'make install' runs.
...
Result: PASS

CPAN.pm's own dependency resolution (the ---- Unsatisfied dependencies detected ---- mechanism) still drives the actual Coy build.

Test plan

• make (build + unit tests): green
• jcpan -t ACME::Error::Coy end-to-end on a freshly cleaned ~/.cpan/build: configure clean, no false have 0, both modules tested, exit 0
• Manual Makefile.PL with a non-existent prereq: prints Warning: prerequisite NoSuchModuleZZZ 1.0 not found. and continues
• Same with PREREQ_FATAL => 1: prints the warning and dies with the upstream MakeMaker FATAL: ... Please install these modules first and rerun 'perl Makefile.PL'. message
• Spot-checked behaviour against system perl Makefile.PL on the same tree — output now matches
• make test-bundled-modules shows 2 pre-existing failures (Net-SSLeay/t/local/33_x509_create_cert.t, Text-CSV/t/55_combi.t) due to missing test helpers (./t/util.pl, Test::Net::SSLeay); unrelated to this change.

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