Drop the externals directory

Nix now requires SQLite and bzip2 to be pre-installed.  SQLite is
detected using pkg-config.  We required DBD::SQLite anyway, so
depending on SQLite is not a big problem.

The --with-bzip2, --with-openssl and --with-sqlite flags are gone.

src/bsdiff-4.3/Makefile.am

@@ -4,10 +4,10 @@ libexec_PROGRAMS = bsdiff bspatch
 
 bsdiff_SOURCES = bsdiff.c
 
-bsdiff_LDADD = ${bzip2_lib}
+bsdiff_LDADD = -lbz2
 
 bspatch_SOURCES = bspatch.c
 
-bspatch_LDADD = ${bzip2_lib}
+bspatch_LDADD = -lbz2
 
-AM_CFLAGS = -O3 ${bzip2_include} ${bsddiff_compat_include}
+AM_CFLAGS = -O3 ${bsddiff_compat_include}

src/libstore/Makefile.am

@@ -10,12 +10,12 @@ pkginclude_HEADERS = \
   globals.hh references.hh pathlocks.hh \
   worker-protocol.hh
 
-libstore_la_LIBADD = ../libutil/libutil.la ../boost/format/libformat.la ${aterm_lib} ${sqlite_lib}
+libstore_la_LIBADD = ../libutil/libutil.la ../boost/format/libformat.la @SQLITE3_LIBS@
 
 EXTRA_DIST = schema.sql
 
 AM_CXXFLAGS = -Wall \
- ${sqlite_include} -I$(srcdir)/.. -I$(srcdir)/../libutil \
+ -I$(srcdir)/.. -I$(srcdir)/../libutil \
  -DNIX_STORE_DIR=\"$(storedir)\" \
  -DNIX_DATA_DIR=\"$(datadir)\" \
  -DNIX_STATE_DIR=\"$(localstatedir)/nix\" \

src/libutil/Makefile.am

@@ -3,7 +3,7 @@ pkglib_LTLIBRARIES = libutil.la
 libutil_la_SOURCES = util.cc hash.cc serialise.cc \
   archive.cc xml-writer.cc immutable.cc
 
-libutil_la_LIBADD = ../boost/format/libformat.la ${aterm_lib} ${sqlite_lib}
+libutil_la_LIBADD = ../boost/format/libformat.la
 
 pkginclude_HEADERS = util.hh hash.hh serialise.hh \
   archive.hh xml-writer.hh types.hh immutable.hh
@@ -11,6 +11,8 @@ pkginclude_HEADERS = util.hh hash.hh serialise.hh \
 if !HAVE_OPENSSL
 libutil_la_SOURCES += \
  md5.c md5.h sha1.c sha1.h sha256.c sha256.h md32_common.h
+else
+libutil_la_LIBADD += @OPENSSL_LIBS@
 endif
 
 AM_CXXFLAGS = -Wall -I$(srcdir)/..