Just wanted to say thanks for the hints. I encountered this strange behaviour when trying to build a linux kernel on Catalina, a simple line based 'make config' was giving segmentation violation. Previously it had all 'just worked' on High Sierra. Adding "export MACOSX_DEPLOYMENT_TARGET=10.14" to my environment variables solved. Replying here in case others fall over this problem.
kevin@Kevins-MBP:~/git/github/linux (linux-5.3.y|✔)$ make V=1 config
/Applications/Xcode.app/Contents/Developer/usr/bin/make -C /Users/kevin/git/github/linux -f /Users/kevin/git/github/linux/Makefile config
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f ./scripts/Makefile.build obj=scripts/basic
gcc -Wp,-MD,scripts/basic/.fixdep.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -o scripts/basic/fixdep scripts/basic/fixdep.c
rm -f .tmp_quiet_recordmcount
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f ./scripts/Makefile.build obj=scripts/kconfig config
gcc -Wp,-MD,scripts/kconfig/.conf.o.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -c -o scripts/kconfig/conf.o scripts/kconfig/conf.c
gcc -Wp,-MD,scripts/kconfig/.confdata.o.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -c -o scripts/kconfig/confdata.o scripts/kconfig/confdata.c
gcc -Wp,-MD,scripts/kconfig/.expr.o.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -c -o scripts/kconfig/expr.o scripts/kconfig/expr.c
flex -oscripts/kconfig/lexer.lex.c -L scripts/kconfig/lexer.l
bison -o/dev/null --defines=scripts/kconfig/parser.tab.h -t -l scripts/kconfig/parser.y
gcc -Wp,-MD,scripts/kconfig/.lexer.lex.o.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -I ./scripts/kconfig -c -o scripts/kconfig/lexer.lex.o scripts/kconfig/lexer.lex.c
bison -oscripts/kconfig/parser.tab.c -t -l scripts/kconfig/parser.y
gcc -Wp,-MD,scripts/kconfig/.parser.tab.o.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -I ./scripts/kconfig -c -o scripts/kconfig/parser.tab.o scripts/kconfig/parser.tab.c
gcc -Wp,-MD,scripts/kconfig/.preprocess.o.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -c -o scripts/kconfig/preprocess.o scripts/kconfig/preprocess.c
gcc -Wp,-MD,scripts/kconfig/.symbol.o.d -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 -c -o scripts/kconfig/symbol.o scripts/kconfig/symbol.c
gcc -o scripts/kconfig/conf scripts/kconfig/conf.o scripts/kconfig/confdata.o scripts/kconfig/expr.o scripts/kconfig/lexer.lex.o scripts/kconfig/parser.tab.o scripts/kconfig/preprocess.o scripts/kconfig/symbol.o
scripts/kconfig/conf --oldaskconfig Kconfig
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
make[2]: *** [config] Segmentation fault: 11
make[1]: *** [config] Error 2
make: *** [sub-make] Error 2
kevin@Kevins-MBP:/cores $ lldb -c core.64998
(lldb) target create --core "core.64998"
Core file '/cores/core.64998' (x86_64) was loaded.
(lldb) bt
* thread #1, stop reason = signal SIGSTOP
* frame #0: 0x00007fff73f91476 libdyld.dylib`stack_not_16_byte_aligned_error