gpgme 1.8 build failure

[Robert J. Hansen]

Build environment: macOS Sierra, XCode 8.1.

quorra:gpgme-1.8.0 rjh$ make
/Applications/Xcode.app/Contents/Developer/usr/bin/make  all-recursive
Making all in src
make[2]: Nothing to be done for `all'.
Making all in tests
Making all in gpg
make[3]: Nothing to be done for `all'.
Making all in gpgsm
make[3]: Nothing to be done for `all'.
Making all in opassuan
make[3]: Nothing to be done for `all'.
make[3]: Nothing to be done for `all-am'.
Making all in doc
/Applications/Xcode.app/Contents/Developer/usr/bin/make  all-am
make[3]: Nothing to be done for `all-am'.
Making all in lang
Making all in cl
make[3]: Nothing to be done for `all'.
Making all in cpp
Making all in src
/bin/sh ../../../libtool  --tag=CXX   --mode=compile g++ -std=c++11
-DHAVE_CONFIG_H -I. -I../../..  -I../../../src -I/usr/local/include
-I/usr/local/include -DBUILDING_GPGMEPP   -g -O2 -MT
keygenerationresult.lo -MD -MP -MF .deps/keygenerationresult.Tpo -c -o
keygenerationresult.lo keygenerationresult.cpp
libtool: compile:  g++ -std=c++11 -DHAVE_CONFIG_H -I. -I../../..
-I../../../src -I/usr/local/include -I/usr/local/include
-DBUILDING_GPGMEPP -g -O2 -MT keygenerationresult.lo -MD -MP -MF
.deps/keygenerationresult.Tpo -c keygenerationresult.cpp  -fno-common
-DPIC -o .libs/keygenerationresult.o
keygenerationresult.cpp:43:23: error: use of undeclared identifier 'strdup'
            res.fpr = strdup(res.fpr);
                      ^
1 error generated.