build: fix -Wunused-but-set-variable support and handle clang better

By default the build used -Wno-unused-but-set-variable but that's
clearly not what we want. Fix those problems.

When using clang, the compiler doesn't error on unknown compile
options, so let's add -Werror to the checking too.

CC='clang'
configure:3408: checking for gcc
configure:3435: result: clang
...
configure:17644: checking whether gcc understands -Wno-unused-but-set-variable
configure:17657: clang -c -Wall -std=gnu89 -g -O2 -Wmissing-declarations -Wmissing-prototypes -Wdeclaration-after-statement -Wstrict-prototypes -Wno-unused-parameter -Wno-sign-compare -Wno-deprecated-declarations -Wno-unused-but-set-variable  conftest.c >&5
warning: unknown warning option '-Wno-unused-but-set-variable'; did you mean '-Wno-unused-const-variable'? [-Wunknown-warning-option]
1 warning generated.
configure:17657: $? = 0
configure:17666: result: yes

Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>

1 files changed, 0 insertions, 20 deletions

diff --git a/src/mm-shared-qmi.c b/src/mm-shared-qmi.c
index a13a2b1c..1e0ae784 100644
--- a/src/mm-shared-qmi.c
+++ b/src/mm-shared-qmi.c
@@ -398,14 +398,10 @@ out:
 static void
 set_current_capabilities_system_selection_preference (GTask *task)
 {
-    MMSharedQmi                                    *self;
-    Private                                        *priv;
     SetCurrentCapabilitiesContext                  *ctx;
     QmiMessageNasSetSystemSelectionPreferenceInput *input;
     QmiNasRatModePreference                         pref;
 
-    self = g_task_get_source_object (task);
-    priv = get_private (MM_SHARED_QMI (self));
     ctx  = g_task_get_task_data (task);
 
     pref = mm_modem_capability_to_qmi_rat_mode_preference (ctx->capabilities);
@@ -919,12 +915,9 @@ set_current_modes_technology_preference_ready (QmiClientNas *client,
                                                GAsyncResult *res,
                                                GTask        *task)
 {
-    SetCurrentModesContext                     *ctx;
     QmiMessageNasSetTechnologyPreferenceOutput *output = NULL;
     GError                                     *error = NULL;
 
-    ctx = g_task_get_task_data (task);
-
     output = qmi_client_nas_set_technology_preference_finish (client, res, &error);
     if (!output ||
         (!qmi_message_nas_set_technology_preference_output_get_result (output, &error) &&
@@ -993,12 +986,9 @@ set_current_modes_system_selection_preference_ready (QmiClientNas *client,
                                                      GAsyncResult *res,
                                                      GTask        *task)
 {
-    SetCurrentModesContext                          *ctx;
     QmiMessageNasSetSystemSelectionPreferenceOutput *output = NULL;
     GError                                          *error = NULL;
 
-    ctx = g_task_get_task_data (task);
-
     output = qmi_client_nas_set_system_selection_preference_finish (client, res, &error);
     if (!output || !qmi_message_nas_set_system_selection_preference_output_get_result (output, &error))
         g_task_return_error (task, error);
@@ -1016,11 +1006,9 @@ set_current_modes_system_selection_preference (GTask *task)
     MMIfaceModem                                   *self;
     SetCurrentModesContext                         *ctx;
     QmiMessageNasSetSystemSelectionPreferenceInput *input;
-    Private                                        *priv;
     QmiNasRatModePreference                         pref;
 
     self = g_task_get_source_object (task);
-    priv = get_private (MM_SHARED_QMI (self));
     ctx  = g_task_get_task_data (task);
 
     input = qmi_message_nas_set_system_selection_preference_input_new ();
@@ -1162,15 +1150,12 @@ get_technology_preference_ready (QmiClientNas *client,
                                  GAsyncResult *res,
                                  GTask        *task)
 {
-    LoadCurrentModesContext                    *ctx;
     LoadCurrentModesResult                     *result = NULL;
     QmiMessageNasGetTechnologyPreferenceOutput *output = NULL;
     GError                                     *error = NULL;
     MMModemMode                                 allowed;
     QmiNasRadioTechnologyPreference             preference_mask;
 
-    ctx = g_task_get_task_data (task);
-
     output = qmi_client_nas_get_technology_preference_finish (client, res, &error);
     if (!output || !qmi_message_nas_get_technology_preference_output_get_result (output, &error)) {
         g_task_return_error (task, error);
@@ -1226,15 +1211,12 @@ load_current_modes_system_selection_preference_ready (QmiClientNas *client,
                                                       GAsyncResult *res,
                                                       GTask        *task)
 {
-    LoadCurrentModesContext                         *ctx;
     LoadCurrentModesResult                          *result = NULL;
     QmiMessageNasGetSystemSelectionPreferenceOutput *output = NULL;
     GError                                          *error = NULL;
     QmiNasRatModePreference                          mode_preference_mask = 0;
     MMModemMode                                      allowed;
 
-    ctx = g_task_get_task_data (task);
-
     output = qmi_client_nas_get_system_selection_preference_finish (client, res, &error);
     if (!output || !qmi_message_nas_get_system_selection_preference_output_get_result (output, &error)) {
         g_task_return_error (task, error);
@@ -4068,7 +4050,6 @@ pds_get_default_tracking_session_ready (QmiClientPds *client,
                                         GAsyncResult *res,
                                         GTask        *task)
 {
-    MMSharedQmi                                  *self;
     SetGpsOperationModeContext                   *ctx;
     QmiMessagePdsSetDefaultTrackingSessionInput  *input;
     QmiMessagePdsGetDefaultTrackingSessionOutput *output;
@@ -4094,7 +4075,6 @@ pds_get_default_tracking_session_ready (QmiClientPds *client,
         return;
     }
 
-    self = g_task_get_source_object (task);
     ctx  = g_task_get_task_data (task);
 
     qmi_message_pds_get_default_tracking_session_output_get_info (