Introduce static_to_shared_library function

The static_to_shared_library function takes an existing static library
and produces a shared library based on it.

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

@@ -26,6 +26,55 @@
 import os
 
 
+def static_to_shared_library(static_lib, shared_lib=None, **kwargs):
+    """
+    Converts a static library to a shared library.
+
+    Parameters:
+        shared_lib (str): Path to the shared library.
+        static_lib (str): Path to the static library.
+
+    Keyword arguments:
+        compiler (str): Path to the compiler. Default is spack_cc.
+        libraries (str list): One or more libraries to link against.
+    """
+    import platform
+
+    arch = platform.system().lower()
+
+    compiler_path = kwargs.get('compiler', spack_cc)
+    libraries = kwargs.get('libraries', [])
+
+    if not shared_lib:
+        shared_lib = '{0}.{1}'.format(os.path.splitext(static_lib)[0],
+                                      dso_suffix)
+
+    compiler = which(compiler_path)
+    compiler_args = []
+
+    if 'linux' in arch:
+        compiler_args = [
+            '-shared',
+            '-Wl,-soname,{0}'.format(os.path.basename(shared_lib)),
+            '-Wl,--whole-archive',
+            static_lib,
+            '-Wl,--no-whole-archive'
+        ]
+    elif 'darwin' in arch:
+        compiler_args = [
+            '-dynamiclib',
+            '-install_name {0}'.format(shared_lib),
+            '-Wl,-force_load,{0}'.format(static_lib)
+        ]
+
+    if len(libraries) > 0:
+        compiler_args.extend(libraries)
+
+    compiler_args.extend(['-o', shared_lib])
+
+    compiler(*compiler_args)
+
+
 class Lua(Package):
     """The Lua programming language interpreter and library."""
 
@@ -58,11 +107,6 @@ class Lua(Package):
         destination="luarocks",
         placement='luarocks')
 
-    # Based on patches from Arch Linux and Homebrew:
-    # https://git.archlinux.org/svntogit/packages.git/tree/trunk/liblua.so.patch?h=packages/lua
-    # https://github.com/Homebrew/homebrew-core/blob/master/Formula/lua.rb
-    patch('liblua-shared.patch')
-
     def install(self, spec, prefix):
         if spec.satisfies("platform=darwin"):
             target = 'macosx'
@@ -76,8 +120,6 @@ def install(self, spec, prefix):
                  spec['ncurses'].prefix.lib),
              'MYLIBS=-lncursesw',
              'CC=%s -std=gnu99' % spack_cc,
-             'LUA_DSO=liblua.%s' % (
-                 dso_suffix),
              target)
         make('INSTALL_TOP=%s' % prefix,
              'MYCFLAGS=%s' % (
@@ -87,10 +129,11 @@ def install(self, spec, prefix):
                  spec['ncurses'].prefix.lib),
              'MYLIBS=-lncursesw',
              'CC=%s -std=gnu99' % spack_cc,
-             'LUA_DSO=liblua.%s' % (
-                 dso_suffix),
              'install')
 
+        static_to_shared_library(join_path(prefix.lib, 'liblua.a'),
+                                 libraries=['-lm'])
+
         with working_dir(os.path.join('luarocks', 'luarocks')):
             configure('--prefix=' + prefix, '--with-lua=' + prefix)
             make('build')