Fix regression in target output file naming logic

Refactoring in commit f4ff60a803 (cmMakefile: Make GetSafeDefinition
return std::string const&, 2018-09-05) accidentally changed the logic
for target artifact prefix and suffix names such that setting a PREFIX
or SUFFIX target property would cause an empty value to be used.  Revert
that part of the change and use a simpler alternative.  Add a test case.

Reported-by: Alan W. Irwin <irwin@beluga.phys.uvic.ca>

2 files changed, 10 insertions, 0 deletions

diff --git a/Tests/OutName/CMakeLists.txt b/Tests/OutName/CMakeLists.txt
new file mode 100644
index 0000000..f024def
--- /dev/null
+++ b/Tests/OutName/CMakeLists.txt
@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.12)
+project(OutName C)
+
+add_executable(OutName main.c)
+set_property(TARGET OutName PROPERTY PREFIX exe.)
+set_property(TARGET OutName PROPERTY SUFFIX .exe)
diff --git a/Tests/OutName/main.c b/Tests/OutName/main.c
new file mode 100644
index 0000000..8488f4e
--- /dev/null
+++ b/Tests/OutName/main.c
@@ -0,0 +1,4 @@
+int main(void)
+{
+  return 0;
+}