Merge bitcoin/bitcoin#24524: doc: remove Boost LDFLAGS from netBSD build docs

8336a06 doc: remove Boost LDFLAGS from netBSD build docs (fanquake)

Pull request description:

  We no-longer link against any Boost libs, so we shouldn't need to use
  any Boost linker flags.

ACKs for top commit:
  hebasto:
    ACK 8336a06, I have reviewed the code and it looks OK, I agree it can be merged. Also verified that there is no other usage of `BOOST_LDFLAGS` in our codebase or documentation.

Tree-SHA512: b7814d10cee789903cb3c613631e184a72f5766cda85261b5f99f9ac207348a2a49c92494c8c1d50163494f6b755c503cf51bf083b31f564dae1b0f493c54c2e

Author: fanquake

doc/build-netbsd.md

@@ -57,7 +57,6 @@ With wallet:
 ./configure --with-gui=no CPPFLAGS="-I/usr/pkg/include" \
     LDFLAGS="-L/usr/pkg/lib" \
     BOOST_CPPFLAGS="-I/usr/pkg/include" \
-    BOOST_LDFLAGS="-L/usr/pkg/lib" \
     BDB_LIBS="-L${BDB_PREFIX}/lib -ldb_cxx-4.8" \
     BDB_CFLAGS="-I${BDB_PREFIX}/include" \
     MAKE=gmake
@@ -70,7 +69,6 @@ Without wallet:
     CPPFLAGS="-I/usr/pkg/include" \
     LDFLAGS="-L/usr/pkg/lib" \
     BOOST_CPPFLAGS="-I/usr/pkg/include" \
-    BOOST_LDFLAGS="-L/usr/pkg/lib" \
     MAKE=gmake
 ```