Fix building latest version of flex (#2401)

* Fix building latest version of flex

* Don't need when clause

* Remove perl deps, shebang too long

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

@@ -25,8 +25,9 @@
 from spack import *
 
 
-class Libsigsegv(Package):
+class Libsigsegv(AutotoolsPackage):
     """GNU libsigsegv is a library for handling page faults in user mode."""
+
     homepage = "https://www.gnu.org/software/libsigsegv/"
     url      = "ftp://ftp.gnu.org/gnu/libsigsegv/libsigsegv-2.10.tar.gz"
 
@@ -34,9 +35,5 @@ class Libsigsegv(Package):
 
     version('2.10', '7f96fb1f65b3b8cbc1582fb7be774f0f')
 
-    def install(self, spec, prefix):
-        configure('--prefix=%s' % prefix,
-                  '--enable-shared')
-
-        make()
-        make("install")
+    def configure_args(self):
+        return ['--enable-shared']