Makevars for installing data.table on Big Sur + Apple Silicon (M1; ARM)

Makevars

# brew --prefix llvm
LLVM_LOC=/usr/local/opt/llvm
# brew --prefix gettext
GETTEXT=/usr/local/opt/gettext
# xcrun --show-sdk-path
XCBASE=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk

CC=$(LLVM_LOC)/bin/clang -fopenmp
CXX=$(LLVM_LOC)/bin/clang++ -fopenmp

CFLAGS=-g -O3 -Wall -pedantic -std=gnu99 -mtune=native -pipe
CXXFLAGS=-g -O3 -Wall -pedantic -std=c++11 -mtune=native -pipe

# more on flags https://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html
LDFLAGS=-L"$(LLVM_LOC)/lib" -L"$(GETTEXT)/lib" --sysroot="$(XCBASE)"
CPPFLAGS=-isystem "$(LLVM_LOC)/include" -isysroot "$(XCBASE)"

Assumes you did the hacky arm homebrew install: https://soffes.blog/homebrew-on-apple-silicon