Merge pull request #676 from stan-dev/updated-ucrt-flags

Manual UCRT config no longer needed on Windows

src/cmdstan-guide/installation.Rmd

@@ -112,7 +112,7 @@ A [CmdStan release](https://github.com/stan-dev/cmdstan/releases) is
 compressed tarfile which contains CmdStan and the Stan and math library submodules.
 The most recent CmdStan release is always available as https://github.com/stan-dev/cmdstan/releases/latest.
 A CmdStan release is versioned by major, minor, patch numbers, e.g., "2.29.2". Please ensure you download
-a tarfile which is named "cmdstan-<version-number" rather than using the "Source Code" links at the bottom of 
+a tarfile which is named "cmdstan-<version-number" rather than using the "Source Code" links at the bottom of
 the release. These are automatically generated by GitHub and do **not** contain the required submodules.
 The release tarfile unpacks into a directory named "cmdstan-<version number>",
 e.g. "cmdstan-2.29.2".
@@ -442,13 +442,6 @@ pacman -Sy mingw-w64-x86_64-make          # 64-bit g++-8
 pacman -Sy mingw-w64-ucrt-x86_64-make     # 64-bit g++-10 (UCRT)
 ```
 
-If you have used the UCRT toolchain,some additional compilation flags will be needed for CmdStan.
-Navigate to the CmdStan/make directory and create a file called `local`. Add the following lines to the file:
-```
-CXXFLAGS += -Wno-nonnull -D_UCRT
-TBB_CXXFLAGS= -D_UCRT
-```
-
 ##### RTools42 & RTools43
 
 Both RTools42 & RTools43 provide 64-bit UCRT toolchains, where RTools42 provides g++-10 and
@@ -480,13 +473,6 @@ Execute the below commands to install the needed dependencies:
 pacman -Sy mingw-w64-ucrt-x86_64-make mingw-w64-ucrt-x86_64-gcc
 ```
 
-Finally, some additional compilation flags will be needed for CmdStan. Navigate to
-the CmdStan/make directory and create a file called `local`. Add the following lines to the file:
-```
-CXXFLAGS += -Wno-nonnull -D_UCRT
-TBB_CXXFLAGS= -D_UCRT
-```
-
 __32-bit Builds__
 
 CmdStan defaults to a 64-bit build. On a 32-bit operating system, you must specify