Fix -j flag earlier

Author: rok

r/inst/build_arrow_static.sh

@@ -114,7 +114,7 @@ ${CMAKE_WRAPPER} ${CMAKE} -DARROW_BOOST_USE_SHARED=OFF \
     -G "${CMAKE_GENERATOR:-Unix Makefiles}" \
     ${SOURCE_DIR}
 
-${CMAKE} --build . --target install --parallel $N_JOBS
+${CMAKE} --build . --target install -- -j"${N_JOBS}"
 
 if command -v sccache &> /dev/null; then
   echo "=== sccache stats after the build ==="

r/tools/nixlibs.R

@@ -539,6 +539,13 @@ build_libarrow <- function(src_dir, dst_dir) {
     j_match <- regmatches(makeflags, regexpr("-j\\s*([0-9]+)", makeflags, perl = TRUE))
     if (length(j_match) > 0) {
       ncores <- as.integer(sub("-j\\s*", "", j_match, perl = TRUE))
+      # Keep GNU make's optional -j argument in one token for nested gmake
+      makeflags <- sub("(^|\\s)-j\\s+([0-9]+)(?=\\s|$)", "\\1-j\\2", makeflags, perl = TRUE)
+      Sys.setenv(MAKEFLAGS = makeflags)
+    } else if (grepl("(^|\\s)-j(\\s|$)", makeflags, perl = TRUE)) {
+      # Give a bare `-j` (e.g. from a parent make's jobserver) an explicit count
+      makeflags <- sub("(^|\\s)-j(\\s|$)", sprintf("\\1-j%s\\2", ncores), makeflags, perl = TRUE)
+      Sys.setenv(MAKEFLAGS = makeflags)
     }
   }
   if (!quietly) {