partial bitcoin#18307: Require pkg-config for all of the hosts

excludes:
- a661449

inapplicable:
- 6fd2118
- 06cfc9c

above two commits are inapplicable as tighter UniValue integration
got rid of that logic altogether, backported as dash#4823

Author: kwvg

configure.ac

@@ -13,6 +13,12 @@ AC_CONFIG_HEADERS([src/config/bitcoin-config.h])
 AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_MACRO_DIR([build-aux/m4])
 
+m4_ifndef([PKG_PROG_PKG_CONFIG], [AC_MSG_ERROR([PKG_PROG_PKG_CONFIG macro not found. Please install pkg-config and re-run autogen.sh])])
+PKG_PROG_PKG_CONFIG
+if test "x$PKG_CONFIG" = x; then
+  AC_MSG_ERROR([pkg-config not found])
+fi
+
 BITCOIN_DAEMON_NAME=dashd
 BITCOIN_GUI_NAME=dash-qt
 BITCOIN_CLI_NAME=dash-cli
@@ -646,13 +652,8 @@ AC_ARG_WITH([daemon],
   [build_bitcoind=$withval],
   [build_bitcoind=yes])
 
-use_pkgconfig=yes
 case $host in
   *mingw*)
-
-     dnl pkgconfig does more harm than good with MinGW
-     use_pkgconfig=no
-
      TARGET_OS=windows
      AC_CHECK_LIB([kernel32], [GetModuleFileNameA],, AC_MSG_ERROR(libkernel32 missing))
      AC_CHECK_LIB([user32],   [main],, AC_MSG_ERROR(libuser32 missing))
@@ -801,16 +802,6 @@ case $host in
      ;;
 esac
 
-if test x$use_pkgconfig = xyes; then
-  m4_ifndef([PKG_PROG_PKG_CONFIG], [AC_MSG_ERROR(PKG_PROG_PKG_CONFIG macro not found. Please install pkg-config and re-run autogen.sh.)])
-  m4_ifdef([PKG_PROG_PKG_CONFIG], [
-  PKG_PROG_PKG_CONFIG
-  if test x"$PKG_CONFIG" = "x"; then
-    AC_MSG_ERROR(pkg-config not found.)
-  fi
-  ])
-fi
-
 if test x$use_extended_functional_tests != xno; then
   AC_SUBST(EXTENDED_FUNCTIONAL_TESTS, --extended)
 fi
@@ -1450,69 +1441,40 @@ if test x$use_tests = xyes; then
   fi
 fi
 
-if test x$use_pkgconfig = xyes; then
-  : dnl
-  m4_ifdef(
-    [PKG_CHECK_MODULES],
-    [
-      if test x$use_qr != xno; then
-        BITCOIN_QT_CHECK([PKG_CHECK_MODULES([QR], [libqrencode], [have_qrencode=yes], [have_qrencode=no])])
-      fi
-      if test x$build_bitcoin_cli$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench != xnononono; then
-        PKG_CHECK_MODULES([EVENT], [libevent >= 2.0.21], [use_libevent=yes], [AC_MSG_ERROR(libevent version 2.0.21 or greater not found.)])
-        if test x$TARGET_OS != xwindows; then
-          PKG_CHECK_MODULES([EVENT_PTHREADS], [libevent_pthreads >= 2.0.21],, [AC_MSG_ERROR(libevent_pthreads version 2.0.21 or greater not found.)])
-        fi
-      fi
-
-      if test "x$use_zmq" = "xyes"; then
-        PKG_CHECK_MODULES([ZMQ],[libzmq >= 4],
-          [AC_DEFINE([ENABLE_ZMQ],[1],[Define to 1 to enable ZMQ functions])],
-          [AC_DEFINE([ENABLE_ZMQ],[0],[Define to 1 to enable ZMQ functions])
-           AC_MSG_WARN([libzmq version 4.x or greater not found, disabling])
-           use_zmq=no])
-      else
-          AC_DEFINE_UNQUOTED([ENABLE_ZMQ],[0],[Define to 1 to enable ZMQ functions])
-      fi
-    ]
-  )
-else
+dnl libevent check
 
-  if test x$build_bitcoin_cli$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench != xnonononono; then
-    AC_CHECK_HEADER([event2/event.h], [use_libevent=yes], AC_MSG_ERROR(libevent headers missing),)
-    AC_CHECK_LIB([event],[main],EVENT_LIBS=-levent,AC_MSG_ERROR(libevent missing))
-    if test x$TARGET_OS != xwindows; then
-      AC_CHECK_LIB([event_pthreads],[main],EVENT_PTHREADS_LIBS=-levent_pthreads,AC_MSG_ERROR(libevent_pthreads missing))
-    fi
+if test x$build_bitcoin_cli$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench != xnonononono; then
+  PKG_CHECK_MODULES([EVENT], [libevent >= 2.0.21], [use_libevent=yes], [AC_MSG_ERROR([libevent version 2.0.21 or greater not found.])])
+  if test x$TARGET_OS != xwindows; then
+    PKG_CHECK_MODULES([EVENT_PTHREADS], [libevent_pthreads >= 2.0.21],, [AC_MSG_ERROR([libevent_pthreads version 2.0.21 or greater not found.])])
   fi
+fi
 
-  if test "x$use_zmq" = "xyes"; then
-     AC_CHECK_HEADER([zmq.h],
-       [AC_DEFINE([ENABLE_ZMQ],[1],[Define to 1 to enable ZMQ functions])],
-       [AC_MSG_WARN([zmq.h not found, disabling zmq support])
-        use_zmq=no
-        AC_DEFINE([ENABLE_ZMQ],[0],[Define to 1 to enable ZMQ functions])])
-     AC_CHECK_LIB([zmq],[zmq_ctx_shutdown],ZMQ_LIBS=-lzmq,
-       [AC_MSG_WARN([libzmq >= 4.0 not found, disabling zmq support])
-        use_zmq=no
-        AC_DEFINE([ENABLE_ZMQ],[0],[Define to 1 to enable ZMQ functions])])
-  else
-    AC_DEFINE_UNQUOTED([ENABLE_ZMQ],[0],[Define to 1 to enable ZMQ functions])
-  fi
+dnl QR Code encoding library check
 
-  if test "x$use_zmq" = "xyes"; then
-    dnl Assume libzmq was built for static linking
-    case $host in
-      *mingw*)
-        ZMQ_CFLAGS="$ZMQ_CFLAGS -DZMQ_STATIC"
-      ;;
-    esac
-  fi
+if test "x$use_qr" != xno; then
+  BITCOIN_QT_CHECK([PKG_CHECK_MODULES([QR], [libqrencode], [have_qrencode=yes], [have_qrencode=no])])
+fi
 
-  if test x$use_qr != xno; then
-    BITCOIN_QT_CHECK([AC_CHECK_LIB([qrencode], [main],[QR_LIBS=-lqrencode], [have_qrencode=no])])
-    BITCOIN_QT_CHECK([AC_CHECK_HEADER([qrencode.h],, have_qrencode=no)])
-  fi
+dnl ZMQ check
+
+if test "x$use_zmq" = xyes; then
+  PKG_CHECK_MODULES([ZMQ], [libzmq >= 4],
+    AC_DEFINE([ENABLE_ZMQ], [1], [Define to 1 to enable ZMQ functions]),
+    [AC_DEFINE([ENABLE_ZMQ], [0], [Define to 1 to enable ZMQ functions])
+    AC_MSG_WARN([libzmq version 4.x or greater not found, disabling])
+    use_zmq=no])
+else
+  AC_DEFINE_UNQUOTED([ENABLE_ZMQ], [0], [Define to 1 to enable ZMQ functions])
+fi
+
+if test "x$use_zmq" = xyes; then
+  dnl Assume libzmq was built for static linking
+  case $host in
+    *mingw*)
+      ZMQ_CFLAGS="$ZMQ_CFLAGS -DZMQ_STATIC"
+    ;;
+  esac
 fi
 
 dnl check if libgmp is present