Set libcurl ssl cert path on linux to allow proper verification of google https certificates. This fixes unit tests and firebase sdk api's to work on linux

PiperOrigin-RevId: 263243424

Author: Googler

app/rest/CMakeLists.txt

@@ -55,6 +55,10 @@ if(MSVC)
       -DWIN32_LEAN_AND_MEAN
       CURL_STATICLIB=1
       )
+elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  set(rest_additional_defines
+      -DFIREBASE_SSL_CAPATH="/etc/ssl/certs"
+      )
 else()
   set(rest_additional_defines)
 endif()

app/rest/transport_curl.cc

@@ -452,6 +452,11 @@ bool BackgroundTransportCurl::PerformBackground(Request* request) {
   CheckOk(curl_easy_setopt(curl_, CURLOPT_SSL_VERIFYPEER, 1L), "verify peer");
   CheckOk(curl_easy_setopt(curl_, CURLOPT_SSL_VERIFYHOST, 2L), "verify host");
 
+#ifdef FIREBASE_SSL_CAPATH
+  CheckOk(curl_easy_setopt(curl_, CURLOPT_CAPATH, FIREBASE_SSL_CAPATH),
+          "CA Path");
+#endif
+
   // Set callback functions.
   CheckOk(curl_easy_setopt(curl_, CURLOPT_HEADERFUNCTION, CurlHeaderCallback),
           "set http header callback");