Fix support for cross-compilation: mysql_config and dtrace

[rdmark]

Description: Fix support cross-compilation
 netatalk fails to cross build from source,
 because it...
  a) fails detecting mysql libraries using mysql_config.
     During cross compilation,
     mysql_config does not work.
  b) runs the build architecture compiler via dtrace.
 .
 This patch makes netatalk consult pkg-config before mysql_config
 and supports exporting the compiler as CC environment variable.
Author: Helmut Grohne <helmut@subdivi.de>
Forwarded: no
Bug-Debian: https://bugs.debian.org/912091
Bug-Debian: https://bugs.debian.org/977570
Last-Update: 2020-12-16
---
This patch header follows DEP-3: http://dep.debian.net/deps/dep3/
--- a/macros/cnid-backend.m4
+++ b/macros/cnid-backend.m4
@@ -120,7 +120,9 @@
     )

     if test -z "$MYSQL_CONFIG" -a -z "$MYSQL_CFLAGS" -a -z "$MYSQL_LIBS" ; then
-        AC_PATH_PROG(MYSQL_CONFIG, mysql_config)
+       PKG_CHECK_MODULES([MYSQL],[mysqlclient],[],[
+          AC_PATH_PROG(MYSQL_CONFIG, mysql_config)
+        ])
     fi

     if test -x "$MYSQL_CONFIG" ; then
--- a/etc/afpd/Makefile.am
+++ b/etc/afpd/Makefile.am
@@ -90,7 +90,7 @@
 DTRACE_OBJ = afpd-afp_dsi.o afpd-fork.o afpd-appl.o afpd-catsearch.o afpd-directory.o afpd-enumerate.o afpd-file.o afpd-filedir.o
 afp_dtrace.o: $(top_srcdir)/include/atalk/afp_dtrace.d $(DTRACE_OBJ)
        if test -f afp_dtrace.o ; then rm -f afp_dtrace.o ; fi
-       $(LIBTOOL) --mode=execute dtrace -G -s $(top_srcdir)/include/atalk/afp_dtrace.d -o afp_dtrace.o $(DTRACE_OBJ)
+       CC=$(CC) $(LIBTOOL) --mode=execute dtrace -G -s $(top_srcdir)/include/atalk/afp_dtrace.d -o afp_dtrace.o $(DTRACE_OBJ)
 afpd_LDADD += afp_dtrace.o @DTRACE_LIBS@
 CLEANFILES += afp_dtrace.o
 endif

[rdmark]

PR in #392