boots extrapath is ignored at building time - as follow:

scons --prefix=/opt/local/mongodb/mongo-client-install --full --extrapath=/opt/local/include/boost --use-system-boost install-mongoclient
scons: Reading SConscript files ...
scons version: 2.3.0
python version: 2 7 6 'final' 0
Checking whether the C++ compiler worksyes
Checking whether the C compiler worksyes
Checking if C++ compiler "g++" is GCC... no
Checking if C++ compiler "g++" is clang... yes
Checking if C compiler "gcc" is clang... yes
Checking if C compiler supports -Wno-unused-local-typedefs... no
Checking if C compiler supports -Wno-unused-function... yes
Checking if C compiler supports -Wno-unused-private-field... yes
Checking if C compiler supports -Wno-deprecated-declarations... yes
Checking if C compiler supports -Wno-tautological-constant-out-of-range-compare... yes
Checking if C compiler supports -Wno-unused-const-variable... yes
Checking if C compiler supports -mmacosx-version-min=10.6... yes
Checking for __thread... no
Checking for C++ header file boost/filesystem/operations.hpp... no
can't find boost headers

Where the "missing" boost/filesystem/operations.hpp file does exist: it's actually located @ /opt/local/include/boost/filesystem/operations.hpp

Looks like the build script is not taking notice of my extrapath...

When I am trying without --use-system-boost the extrapath is used but then the script is blocked later on because --use-system-boost was required by C++ compiler...