fix issues on architectures where char is unsigned per default (arm)

src/gtfs2graph/config/ConfigReader.cpp

@@ -76,7 +76,7 @@ void ConfigReader::read(Config* cfg, int argc, char** argv) const {
                          {"prune-threshold", required_argument, 0, 'p'},
                          {0, 0, 0, 0}};
 
-  char c;
+  int c;
   while ((c = getopt_long(argc, argv, ":hvim:p:", ops, 0)) != -1) {
     switch (c) {
       case 'h':

src/loom/config/ConfigReader.cpp

@@ -109,7 +109,7 @@ void ConfigReader::read(Config* cfg, int argc, char** argv) const {
       {"write-stats", no_argument, 0, 16},
       {0, 0, 0, 0}};
 
-  char c;
+  int c;
   while ((c = getopt_long(argc, argv, ":hvm:D", ops, 0)) != -1) {
     switch (c) {
       case 'h':

src/octi/config/ConfigReader.cpp

@@ -156,7 +156,7 @@ void ConfigReader::read(Config* cfg, int argc, char** argv) const {
                          {"abort-after", required_argument, 0, 'a'},
                          {0, 0, 0, 0}};
 
-  char c;
+  int c;
 
   while ((c = getopt_long(argc, argv, ":hvm:Dg:b:", ops, 0)) != -1) {
     switch (c) {

src/topo/config/ConfigReader.cpp

@@ -95,7 +95,7 @@ void ConfigReader::read(TopoConfig* cfg, int argc, char** argv) const {
 
   double turnRestrDiff = -1;
 
-  char c;
+  int c;
   while ((c = getopt_long(argc, argv, ":hvd:", ops, 0)) != -1) {
     switch (c) {
       case 'h':

src/transitmap/config/ConfigReader.cpp

@@ -118,7 +118,7 @@ void ConfigReader::read(Config* cfg, int argc, char** argv) const {
 
   std::string zoom;
 
-  char c;
+  int c;
   while ((c = getopt_long(argc, argv, ":hvlDz:", ops, 0)) != -1) {
     switch (c) {
       case 'h':