mod_ipv6calc cannot be build with clang / apxs libtool issue

[pbiering]

while libtool honors clang from apxs option call -S CC=clang during --mode compile , it uses unconditional gcc on --mode link

/usr/bin/apxs -S CC=clang -L../lib/ -L../databases/lib/ -lipv6calc_db_wrapper -lipv6calc   -lm -I../ -I../lib/ -I../databases/lib/ -c -Wl,"-lcrypto -ldb -ldb -lcrypto " -Wc,"-O2 -Wall -g -fPIC -D__EXTENSIONS__ -Wformat -Werror -Werror=format-security -Wsizeof-array-argument -Wparentheses-equality -Wextra -Werror=char-subscripts -Wno-deprecated-declarations -Wdate-time -Wno-ignored-optimization-argument" mod_ipv6calc.c
/usr/lib64/apr-1/build/libtool --silent --mode=compile clang -prefer-pic -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS  -fstack-protector-strong  -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer  -DLINUX -D_REENTRANT -D_GNU_SOURCE  -I/usr/include/httpd  -I/usr/include/apr-1   -I/usr/include/apr-1  -O2 -Wall -g -fPIC -D__EXTENSIONS__ -Wformat -Werror -Werror=format-security -Wsizeof-array-argument -Wparentheses-equality -Wextra -Werror=char-subscripts -Wno-deprecated-declarations -Wdate-time -Wno-ignored-optimization-argument -I../ -I../lib/ -I../databases/lib/  -c -o mod_ipv6calc.lo mod_ipv6calc.c && touch mod_ipv6calc.slo
/usr/lib64/apr-1/build/libtool --silent --mode=link clang -Wl,-z,relro -Wl,--as-needed -Wl,-z,now   -Wl,--build-id=sha1   -o mod_ipv6calc.la -lcrypto -ldb -ldb -lcrypto   -L../lib/ -L../databases/lib/ -lipv6calc_db_wrapper -lipv6calc -lm -rpath /usr/lib64/httpd/modules -module -avoid-version    mod_ipv6calc.lo
.libs/mod_ipv6calc.o: file not recognized: file format not recognized
collect2: error: ld returned 1 exit status
apxs:Error: Command failed with rc=65536

bash trace output of --mode link

bash -x /usr/lib64/apr-1/build/libtool --silent --mode=link clang -Wl,-z,relro -Wl,--as-needed -Wl,-z,now   -Wl,--build-id=sha1   -o mod_ipv6calc.la -lcrypto -ldb -ldb -lcrypto   -L../lib/ -L../databases/lib/ -lipv6calc_db_wrapper -lipv6calc -lm -rpath /usr/lib64/httpd/modules -module -avoid-version    mod_ipv6calc.lo
...
+ eval 'gcc -shared  -fPIC -DPIC  .libs/mod_ipv6calc.o   -ldb -lcrypto -L../lib/ -L../databases/lib/ -lipv6calc_db_wrapper -lipv6calc -lm -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -Wl,-z -Wl,relro -Wl,--as-needed -Wl,-z -Wl,now -Wl,--build-id=sha1   -Wl,-soname -Wl,mod_ipv6calc.so -o .libs/mod_ipv6calc.so'
++ gcc -shared -fPIC -DPIC .libs/mod_ipv6calc.o -ldb -lcrypto -L../lib/ -L../databases/lib/ -lipv6calc_db_wrapper -lipv6calc -lm -Wl,-z,now -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -Wl,-z -Wl,relro -Wl,--as-needed -Wl,-z -Wl,now -Wl,--build-id=sha1 -Wl,-soname -Wl,mod_ipv6calc.so -o .libs/mod_ipv6calc.so
.libs/mod_ipv6calc.o: file not recognized: file format not recognized
collect2: error: ld returned 1 exit status
...

any ideas how to fix this?

[pbiering]

Filed bug to Fedora https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=2253786