Added auto-detection of LAPACK/BLAS library names

Added find_libs() to the root Makefile.PL to find libraries in
Debian, Ubuntu, CentOS 7/8, SUSE.

See PDLPorters#15

Signed-off-by: Eric Wheeler <perl-pdl@z.ewheeler.org>

Author: Eric Wheeler

Makefile.PL

@@ -10,6 +10,7 @@ my @pkgs = qw(lapack blas);
 our $libs0 = (
   eval {require PkgConfig; join ' ', map PkgConfig->find($_)->get_ldflags, @pkgs} ||
   eval {require ExtUtils::PkgConfig; join ' ', map ExtUtils::PkgConfig->libs($_), @pkgs} ||
+  find_libs() ||
   `pkg-config @pkgs --libs` ||
   '-L/usr/lib/atlas -llapack -lblas -latlas'
 ) . ' ' . ExtUtils::F77->runtime;
@@ -74,3 +75,45 @@ WriteMakefile(
   dist => { PREOP=>'$(PERL) -MPDL::Core::Dev -e pdlpp_mkgen $(DISTVNAME)' }, # GENERATED subdir in dist tarball
   clean => { FILES => '*~' },
 );
+
+
+sub find_libs
+{
+	return if $^O =~ /MSWin/i;
+
+	my @dirs = split /\s+/, `ldconfig -Nv 2>/dev/null | grep : | cut -f1 -d:`;
+
+	# in performance order based on libraries I've used
+	# for xnec2c in Ubuntu, Debian, SuSE, CentOS, etc.
+	# See comments here for detail:
+	#    https://github.com/KJ7LNW/xnec2c/blob/master/src/mathlib.c#L29
+	my @libs = qw/
+			libopenblaso.so.0 libopenblaso.so libopenblas_openmp.so.0
+			libtatlas.so.3
+			liblapack_atlas.so.3
+			libopenblasp.so.0 libopenblasp.so libopenblas_pthreads.so.0
+			libopenblas.so.0 libopenblas.so libopenblas_serial.so.0
+			libsatlas.so.3
+			liblapacke.so.3
+			libmkl_rt.so/,
+		;
+
+	for my $l (@libs)
+	{
+		for my $d (@dirs)
+		{
+			if ( -e "$d/$l" )
+			{
+				$l =~ s/^lib//;
+				$l =~ s/\..*$//;
+				return "-L$d -l$l"
+			}
+		}
+	}
+
+	foreach (`pkg-config --libs atlas`,
+		`pkg-config --libs lapack`)
+	{
+		return $_ if $_;
+	}
+}