Revert "Fix Fuchsia build error."

This reverts commit c5c3544.

Reason for revert: #59784

Original change's description:
> Fix Fuchsia build error.
>
> TEST=ci
>
> Change-Id: I31c160770bea6ba03fe3ca76545c37ffec94e44e
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401483
> Commit-Queue: Siva Annamalai <[email protected]>
> Reviewed-by: Brian Quinlan <[email protected]>

Change-Id: I302d407a5063a1989d05605e01da71913a8742e7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401902
Reviewed-by: Sigmund Cherem <[email protected]>
Bot-Commit: Rubber Stamper <[email protected]>
Commit-Queue: Ben Konyi <[email protected]>

Author: bkonyi

runtime/bin/process_fuchsia.cc

@@ -511,7 +511,7 @@ class ProcessStarter {
  public:
   ProcessStarter(Namespace* namespc,
                  const char* path,
-                 const char* arguments[],
+                 char* arguments[],
                  intptr_t arguments_length,
                  const char* working_directory,
                  char* environment[],
@@ -540,7 +540,7 @@ class ProcessStarter {
     read_err_ = -1;
     write_out_ = -1;
 
-    program_arguments_ = reinterpret_cast<const char**>(Dart_ScopeAllocate(
+    program_arguments_ = reinterpret_cast<char**>(Dart_ScopeAllocate(
         (arguments_length + 2) * sizeof(*program_arguments_)));
     program_arguments_[0] = const_cast<char*>(path_);
     for (int i = 0; i < arguments_length; i++) {
@@ -795,7 +795,7 @@ class ProcessStarter {
   int read_err_;   // Pipe for stderr to child process.
   int write_out_;  // Pipe for stdin to child process.
 
-  const char** program_arguments_;
+  char** program_arguments_;
   char** program_environment_;
 
   Namespace* namespc_;
@@ -815,7 +815,7 @@ class ProcessStarter {
 
 int Process::Start(Namespace* namespc,
                    const char* path,
-                   const char* arguments[],
+                   char* arguments[],
                    intptr_t arguments_length,
                    const char* working_directory,
                    char* environment[],
@@ -843,7 +843,6 @@ int Process::Start(Namespace* namespc,
 int Process::Exec(Namespace* namespc,
                   const char* path,
                   const char** arguments,
-                  intptr_t arguments_length,
                   const char* working_directory,
                   char* errmsg,
                   intptr_t errmsg_len) {