Don't save unit test reports if run via R CMD check

This was a request from CRAN. The CRAN Repository Policy states:

  Packages should not write in the users' home filespace, nor
  anywhere else on the file system apart from the R session's
  temporary directory (or during installation in the location
  pointed to by TMPDIR: and such usage should be cleaned up).

So check the environment variable set by the Makefile, and only write
reports to file if it specifies that the tests are not being run under
R CMD check.

Fixes #56.

tests/doRUnit.R

@@ -2,13 +2,19 @@
 if(require("RUnit", quietly=TRUE)) {
 
   ## --- Setup ---
+  R_CMD_CHECK <- Sys.getenv("RCMDCHECK") != "FALSE"
 
   pkg <- "TTR" # <-- Change to package name!
 
-  ## Path to unit tests for R CMD check
-  ## PKG.Rcheck/PKG/unitTests
-  path <- system.file("unitTests", package=pkg)
-
+  if (R_CMD_CHECK) {
+    ## Path to unit tests for R CMD check
+    ## PKG.Rcheck/PKG/unitTests
+    path <- system.file("unitTests", package=pkg)
+  } else {
+    ## Path to unit tests for standalone running under Makefile (not R CMD check)
+    ## PKG/tests/../inst/unitTests
+    path <- file.path(getwd(), "..", "inst", "unitTests")
+  }
   cat("\nRunning unit tests\n")
   print(list(pkg=pkg, getwd=getwd(), pathToUnitTests=path))
 
@@ -27,21 +33,25 @@ if(require("RUnit", quietly=TRUE)) {
                                           dirs=path)
   ## Run
   tests <- runTestSuite(testSuite)
-
-  ## Default report name
-  pathReport <- file.path(path, "report")
-
-  ## Report to stdout and text files
+
+  ## Report to stdout
   cat("------------------- UNIT TEST SUMMARY ---------------------\n\n")
   printTextProtocol(tests, showDetails=FALSE)
-  printTextProtocol(tests, showDetails=FALSE,
-                    fileName=paste(pathReport, "Summary.txt", sep=""))
-  printTextProtocol(tests, showDetails=TRUE,
-                    fileName=paste(pathReport, ".txt", sep=""))
-
-  ## Report to HTML file
-  printHTMLProtocol(tests, fileName=paste(pathReport, ".html", sep=""))
-
+
+  ## Report text files (only if not under R CMD check)
+  if (!R_CMD_CHECK) {
+    ## Default report name
+    pathReport <- file.path(path, "report")
+
+    printTextProtocol(tests, showDetails=FALSE,
+                      fileName=paste(pathReport, "Summary.txt", sep=""))
+    printTextProtocol(tests, showDetails=TRUE,
+                      fileName=paste(pathReport, ".txt", sep=""))
+
+    ## Report to HTML file
+    printHTMLProtocol(tests, fileName=paste(pathReport, ".html", sep=""))
+  }
+
   ## Return stop() to cause R CMD check stop in case of
   ##  - failures i.e. FALSE to unit tests or
   ##  - errors i.e. R errors