Merge bitcoin/bitcoin#20201: build: pkg-config related cleanup

c236f2e build: Drop redundant AC_SUBST macros (Hennadii Stepanov)
9049812 build: Drop redundant check of PKG_CHECK_MODULES presence (Hennadii Stepanov)

Pull request description:

  This PR:
  - does not change behavior
  - drops redundant `AC_SUBST` macros

  Also checks of PKG_CHECK_MODULES presence are removed because they are redundant due to the following code https://github.com/bitcoin/bitcoin/blob/ab1feadf4e6cd4f5f2c7e74cea1c7baad61458ba/configure.ac#L16-L20

ACKs for top commit:
  fanquake:
    ACK c236f2e - I see no difference in `config.log`s.

Tree-SHA512: 7ebbfc37123d693e034b8eea4aecbd9ef52b0ea5706b90bd282474e2d61ab0fedc8bca38aa3c9aa88cf2938339b7a491231b11865d39c682d60ef362082f22c5

Author: fanquake

build-aux/m4/bitcoin_find_bdb48.m4

@@ -91,7 +91,6 @@ AC_DEFUN([BITCOIN_FIND_BDB48],[
     fi
   fi
   if test "$use_bdb" != "no"; then
-    AC_SUBST(BDB_LIBS)
     AC_DEFINE([USE_BDB], [1], [Define if BDB support should be compiled in])
     use_bdb=yes
   fi

build-aux/m4/bitcoin_qt.m4

@@ -278,9 +278,7 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   AC_SUBST(QT_LIBS)
   AC_SUBST(QT_LDFLAGS)
   AC_SUBST(QT_DBUS_INCLUDES)
-  AC_SUBST(QT_DBUS_LIBS)
   AC_SUBST(QT_TEST_INCLUDES)
-  AC_SUBST(QT_TEST_LIBS)
   AC_SUBST(QT_SELECT, qt5)
   AC_SUBST(MOC_DEFS)
 ])

configure.ac

@@ -1535,15 +1535,13 @@ dnl libmultiprocess library check
 
 libmultiprocess_found=no
 if test "$with_libmultiprocess" = "yes" || test "$with_libmultiprocess" = "auto"; then
-  m4_ifdef([PKG_CHECK_MODULES], [PKG_CHECK_MODULES([LIBMULTIPROCESS], [libmultiprocess], [
+  PKG_CHECK_MODULES([LIBMULTIPROCESS], [libmultiprocess], [
      libmultiprocess_found=yes;
      libmultiprocess_prefix=`$PKG_CONFIG --variable=prefix libmultiprocess`;
-  ], [true])])
+  ], [true])
 elif test "$with_libmultiprocess" != "no"; then
   AC_MSG_ERROR([--with-libmultiprocess=$with_libmultiprocess value is not yes, auto, or no])
 fi
-AC_SUBST(LIBMULTIPROCESS_CFLAGS)
-AC_SUBST(LIBMULTIPROCESS_LIBS)
 
 dnl Enable multiprocess check
 
@@ -1846,16 +1844,11 @@ AC_SUBST(ENABLE_EXTERNAL_SIGNER)
 AC_SUBST(USE_UPNP)
 AC_SUBST(USE_QRCODE)
 AC_SUBST(BOOST_LIBS)
-AC_SUBST(SQLITE_LIBS)
 AC_SUBST(TESTDEFS)
 AC_SUBST(MINIUPNPC_CPPFLAGS)
 AC_SUBST(MINIUPNPC_LIBS)
 AC_SUBST(NATPMP_CPPFLAGS)
 AC_SUBST(NATPMP_LIBS)
-AC_SUBST(EVENT_LIBS)
-AC_SUBST(EVENT_PTHREADS_LIBS)
-AC_SUBST(ZMQ_LIBS)
-AC_SUBST(QR_LIBS)
 AC_SUBST(HAVE_GMTIME_R)
 AC_SUBST(HAVE_FDATASYNC)
 AC_SUBST(HAVE_FULLFSYNC)