Don't generate import library for shared modules

Also add a test for this on all platforms.

mesonbuild/build.py

@@ -1246,6 +1246,7 @@ class SharedModule(SharedLibrary):
         if 'soversion' in kwargs:
             raise MesonException('Shared modules must not specify the soversion kwarg.')
         super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
+        self.import_filename = None
 
 class CustomTarget(Target):
     known_kwargs = {'input': True,

test cases/linuxlike/7 library versions/installed_files.txt

@@ -7,3 +7,4 @@ usr/lib/libonlyversion.so.1
 usr/lib/libonlyversion.so.1.4.5
 usr/lib/libonlysoversion.so
 usr/lib/libonlysoversion.so.5
+usr/lib/libmodule.so

test cases/linuxlike/7 library versions/meson.build

@@ -43,3 +43,5 @@ test('manually linked 3', executable('manuallink3', out,
 
 test('manually linked 4', executable('manuallink4', out,
   link_args : ['-L.', '-lonlysoversion', rpath_arg]))
+
+shared_module('module', 'lib.c', install : true)

test cases/osx/2 library versions/installed_files.txt

@@ -5,3 +5,4 @@ usr/lib/libonlyversion.dylib
 usr/lib/libonlyversion.1.dylib
 usr/lib/libonlysoversion.dylib
 usr/lib/libonlysoversion.5.dylib
+usr/lib/libmodule.dylib

test cases/osx/2 library versions/meson.build

@@ -39,3 +39,5 @@ test('manually linked 3', executable('manuallink3', out,
 
 test('manually linked 4', executable('manuallink4', out,
   link_args : ['-L.', '-lonlysoversion']))
+
+shared_module('module', 'lib.c', install : true)

test cases/windows/7 mingw dll versioning/installed_files.txt

@@ -8,3 +8,4 @@ usr/bin/libonlysoversion-5.dll
 usr/lib/libonlysoversion.dll.a
 usr/libexec/libcustomdir.dll
 usr/libexec/libcustomdir.dll.a
+usr/lib/libmodule.dll

test cases/windows/7 mingw dll versioning/meson.build

@@ -51,3 +51,5 @@ test('manually linked 4', executable('manuallink4', out,
 shared_library('customdir', 'lib.c',
   install : true,
   install_dir : get_option('libexecdir'))
+
+shared_module('module', 'lib.c', install : true)

test cases/windows/8 msvc dll versioning/installed_files.txt

@@ -10,3 +10,4 @@ usr/bin/onlysoversion-5.dll
 usr/lib/onlysoversion.lib
 usr/libexec/customdir.dll
 usr/libexec/customdir.lib
+usr/lib/module.dll

test cases/windows/8 msvc dll versioning/meson.build

@@ -52,3 +52,5 @@ test('manually linked 4', executable('manuallink4', out,
 shared_library('customdir', 'lib.c',
   install : true,
   install_dir : get_option('libexecdir'))
+
+shared_module('module', 'lib.c', install : true)