See
http://koji.fedoraproject.org/koji/packageinfo?packageID=8350

build.log snippet ...

g++ -DBOOT_BUILD -I../src/include/gen -I../src/include -I../src/vulcan -DNAMESPACE=Vulcan -DNDEBUG -ggdb -DFB_SEND_FLAGS=MSG_NOSIGNAL -DLINUX -DAMD64 -pipe -MMD -fPIC -fmessage-length=0 -O3 -fno-omit-frame-pointer  -pthread -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4  -m64 -mtune=generic -fno-rtti -fno-rtti -fno-rtti  -c ../src/vulcan/RefObject.cpp -o ../temp/boot/vulcan/RefObject.o
g++  -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4  -m64 -mtune=generic -fno-rtti -fno-rtti -Wl,-z,relro  -pthread  -Wl,-rpath,/usr/lib64 -Wl,-rpath,/usr/lib64/firebird/intl ../temp/boot/gpre/cmd.o ../temp/boot/gpre/cme.o ../temp/boot/gpre/cmp.o ../temp/boot/gpre/c_cxx.o ../temp/boot/gpre/exp.o ../temp/boot/gpre/gpre.o ../temp/boot/gpre/hsh.o ../temp/boot/gpre/int_cxx.o ../temp/boot/gpre/jrdmet.o ../temp/boot/gpre/movg.o ../temp/boot/gpre/msc.o ../temp/boot/gpre/par.o ../temp/boot/gpre/pat.o ../temp/boot/gpre/sqe.o ../temp/boot/gpre/sql.o ../temp/boot/gpre/gpre_meta.o ../temp/boot/common/classes/alloc.o ../temp/boot/common/classes/locks.o ../temp/boot/common/classes/semaphore.o ../temp/boot/common/classes/fb_string.o ../temp/boot/common/classes/timestamp.o ../temp/boot/common/classes/PublicHandle.o ../temp/boot/common/classes/TempFile.o ../temp/boot/common/classes/UserBlob.o ../temp/boot/common/classes/SafeArg.o ../temp/boot/common/classes/MsgPrint.o ../temp/boot/common/classes/BaseStream.o ../temp/boot/common/fb_exception.o ../temp/boot/common/thd.o ../temp/boot/common/classes/MetaName.o ../temp/boot/common/StatusHolder.o ../temp/boot/common/classes/init.o ../temp/boot/common/StatusArg.o ../temp/boot/common/utils.o ../temp/boot/config/AdminException.o ../temp/boot/config/Args.o ../temp/boot/config/ArgsException.o ../temp/boot/config/ConfObj.o ../temp/boot/config/ConfObject.o ../temp/boot/config/ConfigFile.o ../temp/boot/config/Configuration.o ../temp/boot/config/Element.o ../temp/boot/config/FileName.o ../temp/boot/config/InputFile.o ../temp/boot/config/InputStream.o ../temp/boot/config/Lex.o ../temp/boot/config/ScanDir.o ../temp/boot/config/Stream.o ../temp/boot/config/StreamSegment.o ../temp/boot/vulcan/PathName.o ../temp/boot/vulcan/RefObject.o ../gen/firebird/lib/libfbstatic.a -o ../gen/firebird/bin/gpre_static -L../gen/firebird/lib -lm -ldl   -lcurses -licuuc -licudata -licui18n
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::utf16ToKey(unsigned short, unsigned short const*, unsigned short, unsigned char*)':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:248: undefined reference to `ucnv_open_50'
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:253: undefined reference to `ucnv_fromUChars_50'
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:256: undefined reference to `ucnv_close_50'
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::utf16LowerCase(unsigned int, unsigned short const*, unsigned int, unsigned short*, unsigned int const*)':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:317: undefined reference to `u_tolower_50'
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::utf16UpperCase(unsigned int, unsigned short const*, unsigned int, unsigned short*, unsigned int const*)':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:383: undefined reference to `u_toupper_50'
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::utf8ToUtf16(unsigned int, unsigned char const*, unsigned int, unsigned short*, unsigned short*, unsigned int*)':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:495: undefined reference to `utf8_nextCharSafeBody_50'
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::utf16Compare(unsigned int, unsigned short const*, unsigned int, unsigned short const*, unsigned short*)':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:643: undefined reference to `u_strCompare_50'
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::utf8WellFormed(unsigned int, unsigned char const*, unsigned int*)':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:719: undefined reference to `utf8_nextCharSafeBody_50'
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::Utf16Collation::stringToKey(unsigned short, unsigned short const*, unsigned short, unsigned char*, unsigned short) const':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:1152: undefined reference to `u_strCompare_50'
../gen/firebird/lib/libfbstatic.a(unicode_util.o): In function `Jrd::UnicodeUtil::utf16Length(unsigned int, unsigned short const*)':
/builddir/build/BUILD/Firebird-2.5.2.26539-0/gen/../src/jrd/unicode_util.cpp:653: undefined reference to `u_countChar32_50'
collect2: error: ld returned 1 exit status