Override bedtools's CXXFLAGS to avoid -g

Remove BT_CXXFLAGS from bioconda's build settings. We do not want -g as
that bloats the executables (on Linux especially), and we do not need -O2
as conda-build's CXXFLAGS already provides suitable optimisation settings.

recipes/bedtools/build.sh

@@ -3,4 +3,4 @@ export CPLUS_INCLUDE_PATH=${PREFIX}/include
 export C_INCLUDE_PATH=${PREFIX}/include
 
 if test -d bedtools2; then echo Hoisting prevented by .*; cd bedtools2; fi
-make install prefix=$PREFIX CXX=$CXX CC=$CC LDFLAGS="-L$PREFIX/lib"
+make install prefix=$PREFIX CXX=$CXX CC=$CC LDFLAGS="-L$PREFIX/lib" BT_CXXFLAGS=