try overriding arch for arm64

Author: kevinushey

src/Makevars.in

@@ -113,6 +113,11 @@ ifeq ($(USE_TBB), SunOS)
   endif
 endif
 
+# Override arch (mainly for arm64 macOS)
+ifneq ("$(ARCH)",)
+MAKE_ARGS += $(ARCH)
+endif
+
 # Write compilation output to file, and log it if installation fails.
 ifeq ($(VERBOSE),)
 	MAKE_ARGS += > tbb.log 2>&1 \

tools/config/configure.R

@@ -64,7 +64,8 @@ switch(
 
 # define special flags for Windows
 db <- configure_database()
-if (Sys.info()[["sysname"]] == "Windows") {
+info <- as.list(Sys.info())
+if (info[["sysname"]] == "Windows") {
 
    cygpath <- nzchar(Sys.which("cygpath"))
    fmt <- if (cygpath) "$(shell cygpath -m \"%s\")" else "%s"
@@ -75,6 +76,14 @@ if (Sys.info()[["sysname"]] == "Windows") {
 
 }
 
+# detect arm64 macOS
+if (info[["sysname"]] == "Darwin") {
+   if (info[["machine"]] == "arm64") {
+      define(ARCH = "arch=arm64")
+   } else {
+      define(ARCH = "")
+   }
+}
 # use c++0x for compatibility with older compilers
 if (getRversion() < "4.0") {
    define(STDVER = "stdver=c++0x")