clarify tbb install log messages

'no tbb libraries found' referred only to shared libraries eligible for
copying, and read as contradicting the subsequent 'creating tbb stub
library (from static tbb)' on toolchains providing only a static TBB.
Say 'runtime libraries' for the copy step, and consistently refer to
the stub as the 'tbb.dll stub', noting what it is built from.

Author: kevinushey

src/install.libs.R

@@ -83,7 +83,7 @@
    if (.Platform$OS.type == "windows" && TBB_ENABLED) {
       tbbDll <- file.path(tbbDest, "tbb.dll")
       if (file.exists(tbbDll)) {
-         writeLines("** tbb.dll already exists; skipping tbb stub library")
+         writeLines("** tbb.dll already exists; skipping tbb.dll stub")
       } else {
          buildTbbStub(tbbDest)
       }
@@ -108,17 +108,17 @@ buildTbbStub <- function(tbbDest) {
 
       # with oneTBB, the stub provides the old TBB ABI's
       # task_scheduler_observer entry point on top of the new runtime
-      writeLines("** creating tbb stub library")
+      writeLines("** creating tbb.dll stub (wrapping the oneTBB runtime)")
       status <- system("R CMD SHLIB -o tbb-compat/tbb.dll tbb-compat/tbb-compat.cpp")
       if (status != 0)
-         stop("error building tbb stub library")
+         stop("error building tbb.dll stub")
 
    } else {
 
       # with older versions of TBB (e.g. Rtools42), tbb-compat.cpp cannot
       # build -- there is no oneTBB runtime to wrap -- but the static
       # library already provides the old ABI, so re-export it wholesale
-      writeLines("** creating tbb stub library (from static tbb)")
+      writeLines("** creating tbb.dll stub (re-exporting the static tbb library)")
 
       tbbLib <- Sys.getenv("TBB_LIB")
       if (!nzchar(tbbLib))
@@ -137,7 +137,7 @@ buildTbbStub <- function(tbbDest) {
       writeLines(command)
       status <- system(command)
       if (status != 0)
-         stop("error building tbb stub library")
+         stop("error building tbb.dll stub")
 
    }
 
@@ -151,10 +151,10 @@ buildTbbStub <- function(tbbDest) {
 # provenance easy to spot in installation logs.
 logTbbLibraries <- function(tbbLibs, source) {
    if (length(tbbLibs)) {
-      fmt <- "** copying tbb libraries from '%s' [%s]"
+      fmt <- "** copying tbb runtime libraries from '%s' [%s]"
       writeLines(sprintf(fmt, source, paste(basename(tbbLibs), collapse = ", ")))
    } else {
-      writeLines(sprintf("** no tbb libraries found in '%s'", source))
+      writeLines(sprintf("** no tbb runtime libraries found in '%s'", source))
    }
 }