compilers: Don't put split soname args in start groups

Some compilers that act as linker drivers (dmd and ldc) need to split
arguments that GCC combines with , (ie, -Wl,-foo,bar -> -L=-foo -L=bar).
As such we need to detect that the previous argument contained -soname,
and not wrap that in a --start-group/--end-group

This modifies the shared library test to demonstrate the problem, with a
test case.

Fixes #6359

mesonbuild/compilers/compilers.py

@@ -569,7 +569,17 @@ class CompilerArgs(collections.abc.MutableSequence):
                 isinstance(self.compiler.linker, (GnuLikeDynamicLinkerMixin, SolarisDynamicLinker))):
             group_start = -1
             group_end = -1
+            is_soname = False
             for i, each in enumerate(new):
+                if is_soname:
+                    is_soname = False
+                    continue
+                elif '-soname' in each:
+                    # To proxy these arguments with D you need to split the
+                    # arguments, thus you get `-L=-soname -L=lib.so` we don't
+                    # want to put the lib in a link -roup
+                    is_soname = True
+                    continue
                 if not each.startswith(('-Wl,-l', '-l')) and not each.endswith('.a') and \
                    not soregex.match(each):
                     continue

test cases/d/3 shared library/lld-test.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python3
+
+import argparse
+import subprocess
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('ldd')
+    parser.add_argument('bin')
+    args = parser.parse_args()
+
+    p, o, _ = subprocess.run([args.ldd, args.bin], stdout=subprocess.PIPE)
+    assert p == 0
+    o = o.decode()
+    assert 'libstuff.so =>' in o, 'libstuff so not in linker path.'
+    assert 'libstuff.so => not found' not in o, 'libstuff.so not found correctly'
+
+
+if __name__ == '__main__':
+    main()

test cases/d/3 shared library/meson.build

@@ -7,7 +7,7 @@ if dc.get_id() == 'gcc'
   endif
 endif
 
-ldyn = shared_library('stuff', 'libstuff.d', install : true)
+subdir('sub')
 ed = executable('app_d', 'app.d', link_with : ldyn, install : true)
 test('linktest_dyn', ed)
 
@@ -19,3 +19,8 @@ pkgc.generate(name: 'test',
           description: 'A test of D attributes to pkgconfig.generate.',
           d_module_versions: ['Use_Static']
 )
+
+ldd = find_program('ldd', required : false)
+if ldd.found()
+  test('ldd-test.py', ed)
+endif

test cases/d/3 shared library/sub/libstuff.d

@@ -0,0 +1,14 @@
+import std.stdio;
+import std.string : format;
+
+export int printLibraryString (string str)
+{
+    writeln ("Library says: %s".format (str));
+    return 4;
+}
+
+version (Windows)
+{
+    import core.sys.windows.dll;
+    mixin SimpleDllMain;
+}

test cases/d/3 shared library/sub/meson.build

@@ -0,0 +1,2 @@
+ldyn = shared_library('stuff', 'libstuff.d', install : true)
+