* installing *source* package ‘udunits2’ ...
** package ‘udunits2’ successfully unpacked and MD5 sums checked
** using staged installation
checking for gcc... clang -mmacosx-version-min=10.13
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether the compiler supports GNU C... yes
checking whether clang -mmacosx-version-min=10.13 accepts -g... yes
checking for clang -mmacosx-version-min=10.13 option to enable C11 features... none needed
checking for XML_ParserCreate in -lexpat... yes
checking for stdio.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for strings.h... yes
checking for sys/stat.h... yes
checking for sys/types.h... yes
checking for unistd.h... yes
checking for udunits2.h... yes
checking for ut_read_xml in -ludunits2... no
-----Error: libudunits2.a not found-----
     If the udunits2 library is installed in a non-standard location,
     use --configure-args='--with-udunits2-lib=/usr/local/lib' for example,
     or --configure-args='--with-udunits2-include=/usr/include/udunits2'
     replacing paths with appropriate values for your installation.
     You can alternatively use the UDUNITS2_INCLUDE and UDUNITS2_LIB
     environment variables.
     If udunits2 is not installed, please install it.
     It is required for this package.
ERROR: configuration failed for package ‘udunits2’
* removing ‘/Volumes/Builds/packages/high-sierra-x86_64/results/4.0/udunits2.Rcheck/udunits2’