always extend link_exe with link flags

otherwise custom link_executable templates do not work

src/dds/toolchain/from_json.cpp

@@ -716,9 +716,9 @@ toolchain dds::parse_toolchain_json_data(const json5::data& dat, std::string_vie
             assert(false && "No link-exe command");
             std::terminate();
         }
-        extend(ret, get_link_flags());
         return ret;
     });
+    extend(tc.link_exe, get_link_flags());
 
     tc.tty_flags = read_opt(tty_flags, [&]() -> string_seq {
         if (!compiler_id) {

src/dds/toolchain/from_json.test.cpp

@@ -93,6 +93,22 @@ TEST_CASE("Generating toolchain commands") {
         "ar rcs stuff.a foo.o bar.o",
         "g++ -fPIC foo.o bar.a -pthread -omeow.exe");
 
+    check_tc_compile("{compiler_id: 'gnu', link_flags: '-mthumb'}",
+                     "g++ -fPIC -pthread -MD -MF foo.o.d -MQ foo.o -c foo.cpp -ofoo.o",
+                     "g++ -fPIC -pthread -Wall -Wextra -Wpedantic -Wconversion "
+                     "-MD -MF foo.o.d -MQ foo.o -c foo.cpp -ofoo.o",
+                     "ar rcs stuff.a foo.o bar.o",
+                     "g++ -fPIC foo.o bar.a -pthread -omeow.exe -mthumb");
+
+    check_tc_compile(
+        "{compiler_id: 'gnu', link_flags: '-mthumb', advanced: {link_executable: 'g++ [in] "
+        "-o[out]'}}",
+        "g++ -fPIC -pthread -MD -MF foo.o.d -MQ foo.o -c foo.cpp -ofoo.o",
+        "g++ -fPIC -pthread -Wall -Wextra -Wpedantic -Wconversion "
+        "-MD -MF foo.o.d -MQ foo.o -c foo.cpp -ofoo.o",
+        "ar rcs stuff.a foo.o bar.o",
+        "g++ foo.o bar.a -omeow.exe -mthumb");
+
     check_tc_compile("{compiler_id: 'msvc'}",
                      "cl.exe /MT /EHsc /nologo /permissive- /showIncludes /c foo.cpp /Fofoo.o",
                      "cl.exe /MT /EHsc /nologo /permissive- /W4 /showIncludes /c foo.cpp /Fofoo.o",