Allow additional environment variables to be set in a clean environment (#5650)

* Allow additional environment variables to be set in a clean environment

* Add documentation for VCPKG_KEEP_ENV_VARS

2 files changed, 20 insertions, 0 deletions

diff --git a/docs/users/config-environment.md b/docs/users/config-environment.md
index f25df89a3..bffa07278 100644
--- a/docs/users/config-environment.md
+++ b/docs/users/config-environment.md
@@ -40,3 +40,10 @@ This environment variable can be set to a triplet name which will be used for un
 #### VCPKG_FORCE_SYSTEM_BINARIES

 

 This environment variable, if set, suppresses the downloading of CMake and Ninja and forces the use of the system binaries.

+

+### VCPKG_KEEP_ENV_VARS

+

+This environment variable can be set to a list of environment variables, separated by `;`, which will be propagated to

+the build environment.

+

+Example: `FOO_SDK_DIR;BAR_SDK_DIR`

diff --git a/toolsrc/src/vcpkg/base/system.cpp b/toolsrc/src/vcpkg/base/system.cpp
index 90b9c34b3..6ddf17496 100644
--- a/toolsrc/src/vcpkg/base/system.cpp
+++ b/toolsrc/src/vcpkg/base/system.cpp
@@ -178,6 +178,19 @@ namespace vcpkg::System
             L"ANDROID_NDK_HOME",
         };
 
+        const Optional<std::string> keep_vars = System::get_environment_variable("VCPKG_KEEP_ENV_VARS");
+        const auto k = keep_vars.get();
+
+        if (k && !k->empty())
+        {
+            auto vars = Strings::split(*k, ";");
+
+            for (auto&& var : vars)
+            {
+                env_wstrings.push_back(Strings::to_utf16(var.c_str()));
+            }
+        }
+
         std::wstring env_cstr;
 
         for (auto&& env_wstring : env_wstrings)