add notes for building on Alpine

README.md

@@ -52,3 +52,7 @@ ENV{ID_SERIAL}=="?*", SYMLINK+="lp/printers/$env{ID_BUS}-$env{ID_SERIAL}"
 
 LABEL="persistent_printer_end"
 ```
+
+extra steps for building on Alpine Linux:
+
+```doas apk add gcc musl-dev autoconf make patch && patch -p0 <lp_server-no-glibc.patch```

lp_server-no-glibc.patch

@@ -0,0 +1,16 @@
+patch to enable compilation on systems that don't use glibc, such as Alpine
+--- src/stty.c
++++ src/stty.c
+@@ -34,6 +34,12 @@
+ 
+ extern int errorcode;
+ 
++#if !defined(EXTA)
++#define EXTA B19200
++#endif
++#if !defined(EXTB)
++#define EXTB B38400
++#endif
+ 
+ #if USE_STTY == SGTTYB
+