fix and test execution of non-empty .bs files

During the build of XS modules, an empty Foo.bs file is normally created
for each Foo.so file. If a Foo_BS file is present, instead this triggers
the auto-generatation of a .bs file which may have executable perl
content.

However, nothing in core currently generates a non-empty .bs file.  So add
a test that this mechanism works, and fix up the three dynamic lib loaders
which implement the 'do $bs if -s $bs' mechanism to not rely on the
process having '.' present in @inc.

As it happens this already works currently, because the name of the
.bs file to load will usually be something like

    ../../lib/auto/Foo/Foo.bs

and the presence of the leading '..' causes 'do' to load the file directly
rather than via @inc.  But locally fix up @inc anyway, in case '../' isn't
always the case.

MANIFEST

@@ -4189,6 +4189,7 @@ ext/Win32CORE/Win32CORE.c	Win32CORE extension
 ext/Win32CORE/Win32CORE.pm	Win32CORE extension (stubs for Win32 CORE subs)
 ext/XS-APItest/APItest.pm	XS::APItest extension
 ext/XS-APItest/APItest.xs	XS::APItest extension
+ext/XS-APItest/APItest_BS	autogenerate APItest.bs
 ext/XS-APItest/core.c		Test API functions when PERL_CORE is defined
 ext/XS-APItest/core_or_not.inc	Code common to core.c and notcore.c
 ext/XS-APItest/exception.c	XS::APItest extension
@@ -4203,6 +4204,7 @@ ext/XS-APItest/t/Block.pm	Helper for ./blockhooks.t
 ext/XS-APItest/t/blockasexpr.t	test recursive descent block parsing
 ext/XS-APItest/t/blockhooks.t	XS::APItest: tests for PL_blockhooks
 ext/XS-APItest/t/blockhooks-csc.t	XS::APItest: more tests for PL_blockhooks
+ext/XS-APItest/t/bootstrap.t	XS::APItest: test APItest.bs
 ext/XS-APItest/t/call.t		Test calling perl from C
 ext/XS-APItest/t/call_checker.t	test call checker plugin API
 ext/XS-APItest/t/caller.t	XS::APItest: tests for caller_cx

dist/XSLoader/XSLoader_pm.PL

@@ -11,7 +11,7 @@ print OUT <<'EOT';
 
 package XSLoader;
 
-$VERSION = "0.26";
+$VERSION = "0.27";
 
 #use strict;
 
@@ -145,7 +145,7 @@ print OUT <<'EOT';
 
     if (-s $bs) { # only read file if it's not empty
 #       print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
-        eval { do $bs; };
+        eval { local @INC = ('.'); do $bs; };
         warn "$bs: $@\n" if $@;
 	goto \&XSLoader::bootstrap_inherit;
     }

ext/DynaLoader/DynaLoader_pm.PL

@@ -85,7 +85,7 @@ package DynaLoader;
 # Tim.Bunce@ig.co.uk, August 1994
 
 BEGIN {
-    $VERSION = '1.41';
+    $VERSION = '1.42';
 }
 
 EOT
@@ -373,7 +373,7 @@ sub bootstrap {
     $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/; # look for .bs 'beside' the library
     if (-s $bs) { # only read file if it's not empty
         print STDERR "BS: $bs ($^O, $dlsrc)\n" if $dl_debug;
-        eval { do $bs; };
+        eval { local @INC = ('.'); do $bs; };
         warn "$bs: $@\n" if $@;
     }
 

ext/XS-APItest/APItest_BS

@@ -0,0 +1,7 @@
+#
+# test that non-empty .bs files get executed
+
+$bscode = <<'EOF';
+$::bs_file_got_executed = 1;
+EOF
+

ext/XS-APItest/t/bootstrap.t

@@ -0,0 +1,17 @@
+#!perl -w
+#
+# check that .bs files are loaded and executed.
+# During build of  XS::APItest, the presence of APItest_BS should
+# cause a non-empty APItest.bs file to auto-generated. When loading
+# APItest.so, the .bs should be automatically executed, which should
+# set $::bs_file_got_executed.
+
+use strict;
+
+use Test::More;
+use XS::APItest;
+
+is $::bs_file_got_executed, 1, "BS file was executed";
+
+done_testing();
+

win32/ce-helpers/makedist.pl

@@ -237,6 +237,7 @@ sub bootstrap {
     my $bs = $file;
     $bs =~ s/(\.\w+)?(;\d*)?$/\.bs/;
     if (-s $bs) { # only read file if it's not empty
+        local @INC = ('.');
         do $bs;
         warn "$bs: $@\n" if $@;
     }