Add external package support to bzip2 (#19343)

* Add external package support to bzip2

* Flake-8

* Flake-8 part 2

Co-authored-by: iarspider <iarpsider@gmail.com>

var/spack/repos/builtin/packages/bzip2/package.py

@@ -3,6 +3,8 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+import re
+
 from spack import *
 
 
@@ -16,6 +18,8 @@ class Bzip2(Package, SourcewarePackage):
     homepage = "https://sourceware.org/bzip2/"
     sourceware_mirror_path = "bzip2/bzip2-1.0.8.tar.gz"
 
+    executables = [r'^bzip2$']
+
     version('1.0.8', sha256='ab5a03176ee106d3f0fa90e381da478ddae405918153cca248e682cd0c4a2269')
     version('1.0.7', sha256='e768a87c5b1a79511499beb41500bcc4caf203726fff46a6f5f9ad27fe08ab2b')
     version('1.0.6', sha256='a2848f34fcd5d6cf47def00461fcb528a0484d8edef8208d6d2e2909dc61d9cd')
@@ -24,6 +28,13 @@ class Bzip2(Package, SourcewarePackage):
 
     depends_on('diffutils', type='build')
 
+    @classmethod
+    def determine_version(cls, exe):
+        output = Executable(exe)('--help', output=str, error=str)
+        match = re.search(r'bzip2, a block-sorting file compressor.'
+                          '  Version ([^,]+)', output)
+        return match.group(1) if match else None
+
     # override default implementation
     @property
     def libs(self):
@@ -95,8 +106,8 @@ def install(self, spec, prefix):
 
             install(lib3, join_path(prefix.lib, lib3))
             with working_dir(prefix.lib):
-                for l in (lib, lib1, lib2):
-                    symlink(lib3, l)
+                for libname in (lib, lib1, lib2):
+                    symlink(lib3, libname)
 
         with working_dir(prefix.bin):
             force_remove('bunzip2', 'bzcat')