build: Remove backticks from configure.ac

Author: fanquake

configure.ac

@@ -555,8 +555,8 @@ case $host in
          dnl It's safe to add these paths even if the functionality is disabled by
          dnl the user (--without-wallet or --without-gui for example).
 
-         bdb_prefix=`$BREW --prefix berkeley-db4 2>/dev/null`
-         qt5_prefix=`$BREW --prefix qt5 2>/dev/null`
+         bdb_prefix=$($BREW --prefix berkeley-db4 2>/dev/null)
+         qt5_prefix=$($BREW --prefix qt5 2>/dev/null)
          if test x$bdb_prefix != x; then
            CPPFLAGS="$CPPFLAGS -I$bdb_prefix/include"
            LIBS="$LIBS -L$bdb_prefix/lib"
@@ -987,7 +987,7 @@ AC_LINK_IFELSE(
         [[ #include <cstdlib> ]],
         [[ int nErr = std::system(""); ]]
     )],
-    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_STD__SYSTEM, 1, Define to 1 if you have the `std::system' function.)],
+    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_STD__SYSTEM, 1, Define to 1 if std::system is available.)],
     [ AC_MSG_RESULT(no) ]
 )
 
@@ -997,11 +997,10 @@ AC_LINK_IFELSE(
         [[ ]],
         [[ int nErr = ::_wsystem(""); ]]
     )],
-    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_WSYSTEM, 1, Define to 1 if you have the `::wsystem' function.)],
+    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_WSYSTEM, 1, Define to 1 if ::wsystem is available.)],
     [ AC_MSG_RESULT(no) ]
 )
 
-# Define to 1 if std::system or ::wsystem (Windows) is available
 AC_DEFINE([HAVE_SYSTEM], [HAVE_STD__SYSTEM || HAVE_WSYSTEM], [std::system or ::wsystem])
 
 LEVELDB_CPPFLAGS=