Merge #12294: [Docs] Create NetBSD build instructions and fix compilation

11c5827 [build] Add NETBSD leveldb target to configure.ac (fanquake)
1944fa3 [doc] Create build-netbsd.md (Randolf Richardson)
336685e [build] Add db4_cxx to bitcoin_find_bdb48.m4 (Randolf Richardson)

Pull request description:

  Replaces #12125.

Tree-SHA512: 411d082ffff7198bcc1b2b6fcdf86c378baf228d8f4fee0e6c9f0688efe9c6b6dcfd5c1ab9c1dfd0c4637723b8584dbbb614634ace0e1a417b59e88a6c736dc0

build-aux/m4/bitcoin_find_bdb48.m4

@@ -64,7 +64,7 @@ AC_DEFUN([BITCOIN_FIND_BDB48],[
   
   if test "x$BDB_LIBS" = "x"; then
     # TODO: Ideally this could find the library version and make sure it matches the headers being used
-    for searchlib in db_cxx-4.8 db_cxx; do
+    for searchlib in db_cxx-4.8 db_cxx db4_cxx; do
       AC_CHECK_LIB([$searchlib],[main],[
         BDB_LIBS="-l${searchlib}"
         break

configure.ac

@@ -662,6 +662,9 @@ case $host in
    *hpux*)
      LEVELDB_TARGET_FLAGS="-DOS_HPUX"
      ;;
+   *netbsd*)
+     LEVELDB_TARGET_FLAGS="-DOS_NETBSD"
+     ;;
    *)
      AC_MSG_ERROR(Cannot build leveldb for $host. Please file a bug report.)
      ;;

doc/build-netbsd.md

@@ -0,0 +1,49 @@
+NetBSD build guide
+======================
+(updated for NetBSD 7.0)
+
+This guide describes how to build bitcoind and command-line utilities on NetBSD.
+
+This guide does not contain instructions for building the GUI.
+
+Preparation
+-------------
+
+You will need the following modules, which can be installed via pkgsrc or pkgin:
+
+```
+autoconf
+automake
+boost
+db4
+git
+gmake
+libevent
+libtool
+python27
+```
+
+Download the source code:
+```
+git clone https://github.com/bitcoin/bitcoin
+```
+
+See [dependencies.md](dependencies.md) for a complete overview.
+
+### Building Bitcoin Core
+
+**Important**: Use `gmake` (the non-GNU `make` will exit with an error).
+
+With wallet:
+```
+./autogen.sh
+./configure CPPFLAGS="-I/usr/pkg/include" LDFLAGS="-L/usr/pkg/lib" BOOST_CPPFLAGS="-I/usr/pkg/include" BOOST_LDFLAGS="-L/usr/pkg/lib"
+gmake
+```
+
+Without wallet:
+```
+./autogen.sh
+./configure --disable-wallet CPPFLAGS="-I/usr/pkg/include" LDFLAGS="-L/usr/pkg/lib" BOOST_CPPFLAGS="-I/usr/pkg/include" BOOST_LDFLAGS="-L/usr/pkg/lib"
+gmake
+```