fix out of tree build

In addition to use ${srcdir} and deliver ${NOTMUCH_SRCDIR} where needed,
source from ruby bindings had to be copied to the out-of-tree target
directory -- if the source files in source directory were referenced
in build and there were also built object files there, those could have
been considered as target files (and then not found when attempting
to create bindings/ruby/notmuch.so).

bindings/Makefile.local

@@ -8,6 +8,7 @@ ifeq ($(HAVE_RUBY_DEV),1)
 	cd $(dir)/ruby && \
 		EXTRA_LDFLAGS="$(NO_UNDEFINED_LDFLAGS)" \
 		LIBNOTMUCH="../../lib/$(LINKER_NAME)" \
+		NOTMUCH_SRCDIR='$(NOTMUCH_SRCDIR)' \
 		ruby extconf.rb --vendor
 	$(MAKE) -C $(dir)/ruby
 endif

bindings/ruby/extconf.rb

@@ -5,7 +5,7 @@
 
 require 'mkmf'
 
-dir = File.join('..', '..', 'lib')
+dir = File.join(ENV['NOTMUCH_SRCDIR'], 'lib')
 
 # includes
 $INCFLAGS = "-I#{dir} #{$INCFLAGS}"

configure

@@ -47,6 +47,12 @@ if [ "$srcdir" != "." ]; then
     # Emacs only likes to generate compiled files next to the .el files
     # by default so copy these as well (which is not ideal).
     cp -a "$srcdir"/emacs/*.el emacs
+
+    # We were not able to create fully working Makefile using ruby mkmf.rb
+    # so ruby bindings source files are copied as well (ditto -- not ideal).
+    mkdir bindings/ruby
+    cp -a "$srcdir"/bindings/ruby/*.[ch] bindings/ruby
+    cp -a "$srcdir"/bindings/ruby/extconf.rb bindings/ruby
 fi
 
 # Set several defaults (optionally specified by the user in
@@ -357,8 +363,8 @@ int main(void) {
     return 0;
 }
 EOF
-if ${CC} ${CFLAGS} _libversion.c -o _libversion > /dev/null 2>&1 && \
-       ./_libversion > _libversion.sh && . ./_libversion.sh
+if ${CC} ${CFLAGS} -I"$srcdir" _libversion.c -o _libversion > /dev/null 2>&1 \
+       && ./_libversion > _libversion.sh && . ./_libversion.sh
 then
     printf "OK.\n"
 else