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CFLAGS and LDFLAGS configuration problem

Hello! I have the following problem: i using Red Hat Enterprise 5.
I want to build and install cairo to the folder differrent from /usr/local. So i using the following statement:
./configure --prefix=/opt CFLAGS=-I/opt/include LDFLAGS=-L/opt/lib
after configuring the configure script write me the following information message:
using CFLAGS:
-I/usr/include/freetype2 -I/usr/local/include -I/usr/include/libpng12 -I/usr/local/include -I/usr/local/include...
However i have the freetype2 in /opt/include/. So i don't understand why configure script ignore the CFLAGS, when i set the location to my freetype in opt folder?
My PKG_CONFIG_PATH is:
PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:/usr/lib/pkgconfig"
LD_LIBRARY_PATH="/usr/local/lib:/usr/lib"

However if add before the configure script execution, the line:
export PKG_CONFIG_PATH=/opt/lib/pkgconfig
and then:
./configure --prefix=/opt CFLAGS=-I/opt/include LDFLAGS=-L/opt/lib
It will use the expected path to freetype:
using CFLAGS:
-I/opt/include/freetype2 -I/opt/include -I/usr/include/libpng12.
So how CFLAGS work?

You don't need to use CFLAGS to build cairo in to opt. CFLAGS are normaly use to optimization flags or debugging.

You can simple ./configure --prefix=/opt

PS: My answer is incomplete.

./configure --help gives:

Code:

 FONTCONFIG_CFLAGS

              C compiler flags for FONTCONFIG, overriding pkg-config

  FONTCONFIG_LIBS

              linker flags for FONTCONFIG, overriding pkg-config

  FREETYPE_CFLAGS

              C compiler flags for FREETYPE, overriding pkg-config

  FREETYPE_LIBS

              linker flags for FREETYPE, overriding pkg-config

So it's to assume you have to work with FREETYPE_CFLAGS and FREETYPE_LIBS

PS: I've made a test compile and I believe it's FREETYPE_CFLAGS that you want.

Thank you very much for your answer. Using FREETYPE_CFLAGS and FREETYPE_LIBS solve my problem.My mistake was that i simply thought that CFLAGS and LDFLAGS override the pkg-config