In several places, the standard Fedora linker flags (LDFLAGS) from redhat-rpm-config are not used for linking DSOs:

gcc  -DMAX_STACK_ALLOC=2048 -Wall -m64 -DF_INTERFACE_GFORT -fPIC -DDYNAMIC_ARCH -DNO_WARMUP -DMAX_CPU_NUMBER=128 -DASMNAME= -DASMFNAME=_ -DNAME=_ -DCNAME= -DCHAR_NAME=\"_\" -DCHAR_CNAME=\"\" -I..  -shared -o ../libRblas.so \
-Wl,--whole-archive ../libRblas-r0.2.20.a -Wl,--no-whole-archive \
-Wl,-soname,libRblas.so -lm -lgfortran -lm -lgfortran

gcc -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -mcet -fcf-protection -fPIC -DMAX_STACK_ALLOC=2048 -Wall -m64 -DF_INTERFACE_GFORT -fPIC -DDYNAMIC_ARCH -DNO_WARMUP -DMAX_CPU_NUMBER=128 -DASMNAME= -DASMFNAME=_ -DNAME=_ -DCNAME= -DCHAR_NAME=\"_\" -DCHAR_CNAME=\"\" -I..  -shared -o ../libopenblas-r0.2.20.so \
-Wl,--whole-archive ../libopenblas-r0.2.20.a -Wl,--no-whole-archive \
-Wl,-soname,libopenblas.so.0 -lm -lgfortran -lm -lgfortran

Flags such as -Wl,-z,relro -specs=/usr/lib/rpm/redhat/redhat-hardened-ld are missing.

There are just examples from the build log, other DSOs are affected as well.

See https://src.fedoraproject.org/rpms/redhat-rpm-config/blob/master/f/buildflags.md for information on RPM macros and environment variables provided by the build environment.