emscripten: use single arguments when specifying options

i.e. without a space between the "-s" and option name. See:
https://github.com/emscripten-core/emscripten/issues/11463

This is supported since Emscripten 1.39.19, see:
f45bea21f3

cross/wasm.txt

@@ -5,9 +5,9 @@ ar = '/home/jpakkane/src/emsdk/upstream/emscripten/emar'
 
 [built-in options]
 c_args = []
-c_link_args = ['-s','EXPORT_ALL=1']
+c_link_args = ['-sEXPORT_ALL=1']
 cpp_args = []
-cpp_link_args = ['-s', 'EXPORT_ALL=1']
+cpp_link_args = ['-sEXPORT_ALL=1']
 
 [host_machine]
 

mesonbuild/compilers/mixins/emscripten.py

@@ -65,7 +65,7 @@ class EmscriptenMixin(Compiler):
         args = ['-pthread']
         count: int = env.coredata.options[OptionKey('thread_count', lang=self.language, machine=self.for_machine)].value
         if count:
-            args.extend(['-s', f'PTHREAD_POOL_SIZE={count}'])
+            args.append(f'-sPTHREAD_POOL_SIZE={count}')
         return args
 
     def get_options(self) -> 'coredata.MutableKeyedOptionDictType':

mesonbuild/linkers/linkers.py

@@ -889,10 +889,10 @@ class WASMDynamicLinker(GnuLikeDynamicLinkerMixin, PosixDynamicLinkerMixin, Dyna
     id = 'ld.wasm'
 
     def get_allow_undefined_args(self) -> T.List[str]:
-        return ['-s', 'ERROR_ON_UNDEFINED_SYMBOLS=0']
+        return ['-sERROR_ON_UNDEFINED_SYMBOLS=0']
 
     def no_undefined_args(self) -> T.List[str]:
-        return ['-s', 'ERROR_ON_UNDEFINED_SYMBOLS=1']
+        return ['-sERROR_ON_UNDEFINED_SYMBOLS=1']
 
     def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
                         suffix: str, soversion: str, darwin_versions: T.Tuple[str, str]) -> T.List[str]: