fix bug where sometimes an existing installation of flac could interfere with the build process (SF#1763690: https://sourceforge.net/tracker/index.php?func=detail&aid=1763690&group_id=13478&atid=113478)
diff --git a/configure.in b/configure.in
index 3c9aac8..8826f19 100644
--- a/configure.in
+++ b/configure.in
@@ -274,17 +274,17 @@
 AH_TEMPLATE(FLAC__HAS_GAS, [define if you are compiling for PowerPC and have the 'gas' assembler])
 fi
 
-OUR_CFLAGS_HEAD='-I$(top_builddir) -I$(srcdir)/include -I$(top_srcdir)/include'
+CPPFLAGS='-I$(top_builddir) -I$(srcdir)/include -I$(top_srcdir)/include'" $CPPFLAGS"
 if test "x$debug" = xtrue; then
-	OUR_CFLAGS_HEAD="$OUR_CFLAGS_HEAD -g -DDEBUG"
+	CPPFLAGS="-DDEBUG $CPPFLAGS"
+	CFLAGS="-g $CFLAGS"
 else
-	OUR_CFLAGS_HEAD="$OUR_CFLAGS_HEAD -DNDEBUG"
+	CPPFLAGS="-DNDEBUG $CPPFLAGS"
 	if test "x$GCC" = xyes; then
-		OUR_CFLAGS_HEAD="$OUR_CFLAGS_HEAD -O3 -funroll-loops -finline-functions -Wall -W -Winline -DFLaC__INLINE=__inline__"
+		CPPFLAGS="-DFLaC__INLINE=__inline__ $CPPFLAGS"
+		CFLAGS="-O3 -funroll-loops -finline-functions -Wall -W -Winline $CFLAGS"
 	fi
 fi
-CFLAGS="$OUR_CFLAGS_HEAD $CFLAGS"
-CXXFLAGS="$OUR_CFLAGS_HEAD $CXXFLAGS"
 
 #@@@
 AM_CONDITIONAL(FLaC__HAS_AS__TEMPORARILY_DISABLED, test "yes" = "no")
diff --git a/doc/html/changelog.html b/doc/html/changelog.html
index 7fba15e..492ef9f 100644
--- a/doc/html/changelog.html
+++ b/doc/html/changelog.html
@@ -98,6 +98,7 @@
 				build system:
 				<ul>
 					<li>Fixed bug compiling <span class="commandname">flac</span> without Ogg support (<a href="https://sourceforge.net/tracker/index.php?func=detail&amp;aid=1760786&amp;group_id=13478&amp;atid=113478">SF #1760786</a>).</li>
+					<li>Fixed bug where sometimes an existing installation of flac could interfere with the build process (<a href="https://sourceforge.net/tracker/index.php?func=detail&amp;aid=1763690&amp;group_id=13478&amp;atid=113478">SF #1763690</a>).</li>
 				</ul>
 			</li>
 			<li>