R package C++ compile can't find header

[Jason Bacon <outpaddling%yahoo.com@localhost>]

Anybody seen an error like this before?  The C++ command appears to be 
specifying the correct include path, but reports that it can't find the 
header file.

The package is in wip/R-readxl.

Thanks,

    JB

* installing *source* package 'readxl' ...
** package 'readxl' successfully unpacked and MD5 sums checked
** libs
c++ -I"/sharedapps/pkg-2018Q2/lib/R/include" -DNDEBUG -Iunix -I. 
-fvisibility=hidden 
-I"/home/sharedapps/pkg-2018Q2/lib/R/library/Rcpp/include" 
-I/sharedapps/pkg-2018Q2/include -I/usr/include 
-I/sharedapps/pkg-2018Q2/include/glib/glib-2.0 
-I/sharedapps/pkg-2018Q2/include/glib/gio-unix-2.0 
-I/sharedapps/pkg-2018Q2/lib/glib-2.0/include 
-I/sharedapps/pkg-2018Q2/include/freetype2 
-I/sharedapps/pkg-2018Q2/include/libdrm 
-I/sharedapps/pkg-2018Q2/include/ncurses   -fpic  -O2 -pthread 
-I/sharedapps/pkg-2018Q2/include -I/usr/include 
-I/sharedapps/pkg-2018Q2/include/glib/glib-2.0 
-I/sharedapps/pkg-2018Q2/include/glib/gio-unix-2.0 
-I/sharedapps/pkg-2018Q2/lib/glib-2.0/include 
-I/sharedapps/pkg-2018Q2/include/freetype2 
-I/sharedapps/pkg-2018Q2/include/libdrm 
-I/sharedapps/pkg-2018Q2/include/ncurses  -c RcppExports.cpp -o 
RcppExports.o
RcppExports.cpp:4:18: fatal error: Rcpp.h: No such file or directory
compilation terminated.
*** Error code 1

Stop.
make: stopped in /home/sharedapps/pkgsrc-2018Q2/wip/R-readxl/work/readxl/src
ERROR: compilation failed for package 'readxl'
* removing 
'/home/sharedapps/pkgsrc-2018Q2/wip/R-readxl/work/.destdir/sharedapps/pkg-2018Q2/lib/R/library/readxl'
*** Error code 1

Stop.
bmake.bin[1]: stopped in /sharedapps/pkgsrc-2018Q2/wip/R-readxl
*** Error code 1

Stop.
bmake.bin: stopped in /sharedapps/pkgsrc-2018Q2/wip/R-readxl

[root@centosdev R-readxl]# ls 
/home/sharedapps/pkg-2018Q2/lib/R/library/Rcpp/include/
doxygen  Rcpp  RcppCommon.h  Rcpp.h