Add a test

We also don't want to skip empty string because if a user specifies
an empty string, it is their intention whatever that intention is.

src/cmdline.cc

@@ -422,15 +422,13 @@ static std::vector<std::string_view>
 split_by_comma_or_colon(std::string_view str) {
   std::vector<std::string_view> vec;
 
-  while (!str.empty()) {
+  for (;;) {
     i64 pos = str.find_first_of(",:");
     if (pos == str.npos) {
       vec.push_back(str);
       break;
     }
-    if (pos > 0) {
-      vec.push_back(str.substr(0, pos));
-    }
+    vec.push_back(str.substr(0, pos));
     str = str.substr(pos + 1);
   }
   return vec;

test/exclude-libs.sh

@@ -48,6 +48,12 @@ readelf --dyn-syms $t/f.so > $t/log
 ! grep -Fq bar $t/log || false
 grep -Fq baz $t/log
 
+$CC -B. -shared -o $t/f.so $t/e.o $t/c.a $t/d.a -Wl,-exclude-libs=c.a:d.a
+readelf --dyn-syms $t/f.so > $t/log
+! grep -Fq foo $t/log || false
+! grep -Fq bar $t/log || false
+grep -Fq baz $t/log
+
 $CC -B. -shared -o $t/f.so $t/e.o $t/c.a $t/d.a -Wl,-exclude-libs=ALL
 readelf --dyn-syms $t/f.so > $t/log
 ! grep -Fq foo $t/log || false