R-Rcpp fails to build on Tiger: fatal error: execinfo.h: No such file or directory

[barracuda156]

* installing *source* package ‘Rcpp’ ...
** package ‘Rcpp’ successfully unpacked and MD5 sums checked
** using staged installation
** libs
/opt/local/bin/g++-mp-7 -std=gnu++14 -I"/opt/local/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include/  -isystem/opt/local/include/LegacySupport -I/opt/local/include   -fPIC  -pipe -Os -arch ppc  -c api.cpp -o api.o
In file included from ../inst/include/Rcpp.h:59:0,
                 from api.cpp:26:
../inst/include/Rcpp/exceptions_impl.h:38:12: fatal error: execinfo.h: No such file or directory
 #  include <execinfo.h>
            ^~~~~~~~~~~~
compilation terminated.
make: *** [api.o] Error 1
ERROR: compilation failed for package ‘Rcpp’

[barracuda156]

In 73f8086518f96e2ac625ef6d5d5af8275f839971/macports-ports (master):

R-Rcpp: fix for 10.4

Fixes: #67254