There is no _nl_msg_cat_cntr in musl libc and optimizations
based upon its unchanged value are not possible.

--- a/snapper/Regex.cc
+++ b/snapper/Regex.cc
@@ -22,7 +22,9 @@
 #include <stdexcept>
 #include "snapper/Regex.h"
 
+#if defined(__GLIBC__)
 extern int _nl_msg_cat_cntr;
+#endif
 
 
 namespace snapper
@@ -40,7 +42,9 @@
 	regerror(errcode, &rx, error, esize);
 	throw std::runtime_error(string("Regex compilation error: ") + error);
     }
+#if defined(__GLIBC__)
     my_nl_msg_cat_cntr = _nl_msg_cat_cntr;
+#endif
     rm = new regmatch_t[nm];
 }
 
@@ -55,11 +59,15 @@
 bool
 Regex::match (const string& str, int eflags) const
 {
+#if defined(__GLIBC__)
     if (my_nl_msg_cat_cntr != _nl_msg_cat_cntr) {
+#endif
 	regfree (&rx);
 	regcomp (&rx, pattern.c_str (), cflags);
+#if defined(__GLIBC__)
 	my_nl_msg_cat_cntr = _nl_msg_cat_cntr;
     }
+#endif
 
     last_str = str;